Process and device for in-air production of single droplets, compound droplets, and shape-controlled (compound) particles or fibers

ABSTRACT

A production process and a related device comprises a formation process comprising: contacting a first liquid material and a second liquid material with each other at a contact point in a gas atmosphere, wherein at the contact point at least one of the first liquid material and the second liquid material is provided as a liquid jet propagating in a direction, to provide at the contact point a third jet of a coalesced third material propagating in a third direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase under 35 USC 371 of InternationalApplication No. PCT/EP2017/057392 filed on Mar. 29, 2017, which claimspriority to European Application No. 16163060.3 filed Mar. 30, 2016,European Application No. 16163461.3 Mar. 31, 2016, and EuropeanApplication No. 16181763.0 filed Jul. 28, 2016, the contents of whichare hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to a process for the production of a material,such as a fibrous material or a particulate material (or a dispersedmaterial). The invention further relates to device for executing suchprocess. Yet further, the invention also relates to a product obtainableby such process and/or with such device.

BACKGROUND OF THE INVENTION

Particulate generation systems are known in the art. US 20120107498, forinstance, describes a multi-component particle generating system thatmay include a first nozzle constructed to generate at least one isolatedparticle, and a second nozzle arranged to generate a generallyuninterrupted fluid jet without breaking up. The first and secondnozzles are arranged to have the isolated particle traverse the fluidjet from one side to the other side so as to combine the particle withfluid of the second fluid jet, for providing a multi component particle.A collector is arranged on the other side of the fluid jet by which theisolated particles can be captured after collision with the fluid jet.The system includes a modulator, for modulating the second fluid jet soas to provide an undulated jet having thicker and thinner portions.

WO2015/091641 relates to a method for producing polyamides by means of aspray nozzle arrangement for the collision of spray jets, comprising atleast one spray nozzle forming a first spray jet having a first sprayjet cross-sectional surface and a first spray jet longitudinal extensionaxis, and comprising a second spray jet forming a second spray jethaving a second spray jet cross-sectional surface and a second spray jetlongitudinal extension axis, wherein the first and second spray jetshave a spray direction that is facing the gravitational field, and arearranged opposite one another such that in a spray direction facing thegravitational field, the formed spray jets collide in a collision area.

SUMMARY OF THE INVENTION

Today, additive manufacturing (AM, also known as 3D printing) enablesfast and high-quality prototyping, production of lightweight metalparts, and construction of artificial human tissues. In most AMprocesses, a small amount of material is ejected and deposited toconstitute a printed product. However, though liquids can be easilyprocessed, only solids maintain their shape after deposition. Therefore,in order to accommodate the properties of different material groups,various AM techniques have been developed. For example, ink-jet printingis suitable for deposition of low-viscosity liquids, extrusion printingfor medium-viscosity plastics and cell-containing hydrogels, and solidsand pastes can be processed using laser transfer, where a focused laserpulse drives the ejection of a “voxel” (volume pixel) of from a thinfilm. However, these technologies not only pose severe trade-offs interms of resolution and throughput, they also fail to integrate solid,soft, and liquid phases within a single 3D-printed product.

In contrast, microfluidics allows for in-line processing: to manipulatefluids after ejection from a nozzle but prior to their collection oranalysis. Here, small quantities of liquid, solid, or gaseous materialare merged, separated or even formed in channels on a chip, by optical,electronic, or mechanical manipulations. This versatility has resultedin tremendous progress and integration of research in engineering,physics, chemistry, biology, and healthcare. However, three keylimitations affect widespread application of microfluidics devices.First, microfluidics chips are usually operated at flow rates in theorder of 10 μl /min, which ensures optimal flow control and preventsexcessive pressure build-up resulting in device damage, but which is toolow for many practical purposes. Second, microfluidic “base units” (e.g.droplets, particles, and fibers) are typically produced using a separatelow-viscosity coaxial flow to induce emulsification (in dropletmicrofluidics) or to prevent clogging (in continuous micro fluidics).Therefore, one-step deposition of base units to form larger,shape-stable structures is hardly feasible. Even if this co-flow couldbe omitted, the liquid velocity at a microfluidic device exit would betoo low to obtain jetting, which is the principle behind common printingtechnologies. Third, challenges regarding the design, manufacture,surface treatment and operation of microfluidic devices hamper theirrapid prototyping and scaling, and therefore delay process optimizationthat could drive widespread application of microfluidic technologies.

Hence, it is an aspect of the invention to provide an alternativeproduction process, which preferably further at least partly obviatesone or more of above-described drawbacks, which may be relatively simpleand/or which may be relatively easily implementable. Further, it is anobjective of the invention to provide a device able to generate materialin gas, i.e. in a gaseous atmosphere (especially including a lowvacuum). The present invention may have as object to overcome orameliorate at least one of the disadvantages of the prior art, or toprovide a useful alternative.

The invention is related to a microfluidic strategy substantiallycompletely performed in a gaseous atmosphere (“in air”) in contrast to aliquid surrounding, as most microfluidic strategies are related to.Hence, the strategy (and related production process) described hereinmay be described as in-gas microfluidics. Especially, the productionprocess may be performed in air since air may be abundantly available.Hence the strategy and production process may also be referred to hereinas in-air microfluidics (IAMF). Moreover, the acronym “IAMF” and theterm “in-air microfluidics” used below do not exclude the use of anyother gaseous atmospheres than air. Especially, the terms “in-gas”, “ina gas atmosphere”, “in a gaseous atmosphere”, and “in-air” are usedherein as completely interchangeable. If, for instance, the strategy isused to prepare material of which the (semi-) product or the startingmaterial may be susceptible to oxidation, a nitrogen atmosphere may beused or the atmosphere may consist of a noble gas. Also these gaseousatmospheres are comprised by the term “in-air” microfluidics and “IAMF”herein.

Especially, in the in-gas or in-air microfluidics, the key benefits ofAM may be combined with those of micro fluidics. In particular, IAMFenables high throughputs, oil-free micro-particle production and directcontact-free deposition of liquids and solids onto arbitrary substrates,or receptor elements, while offering in-line control of material phaseand shape as exploited in chip-based microfluidics. A relevant featureof IAMF is to merge physically or chemically interacting (reacting)liquids after ejection in flight, in the gaseous atmosphere prior toimpact with any receptor element, similar to microfluidics and hence thename. However, the flow is governed by partly different mechanisms ascompared to microfluidics, since air or another gas is used as aseparating phase. After in-gas coalescence, the processed material mayespecially be collected in a bath to produce microfluidics base units,or be deposited onto a solid surface to “print” (partly) solid or liquidmaterials, such as to coat another material, for 2D patterning, e.g. forproducing material libraries, and to generate (complex) 3-dimensionalbodies.

Hence, in a first aspect, the invention provides a production processcomprising a formation process, the formation process comprising:contacting a first liquid material and a second liquid material witheach other at a contact point in a gas atmosphere, wherein at thecontact point at least one of the first liquid material and the secondliquid material is provided as a liquid jet propagating in a (respectivejet) direction, to provide at the contact point a third jet of acoalesced third material (“third material”) propagating in a thirddirection.

The first liquid material and the second liquid material essentiallycontact each other at the (mutual) contact point to provide the(coalesced) third material.

The process may comprise directing a first liquid jet comprising thefirst liquid material to a (virtual) collision point in the gasatmosphere, and directing a second liquid jet comprising the secondliquid material to the (virtual) collision point, to provide at thecollision point the (coalesced) third material. Especially, the contactpoint comprises the collision point. Such embodiments of the process(especially wherein at least two jets collide at a collision point)especially relate to an “in-flight” formation process.

The process may alternatively (and additionally, see below) comprise an“indirect contacting formation” process. Especially the indirectcontacting formation process comprises: providing a second liquid jetcomprising the second liquid material by a second liquid providingdevice comprising a second device face and a second device opening,wherein the second liquid jet is directed with a second liquid jetdirection, and providing the first liquid material to the second deviceface at a position above said second device opening, and allowing thefirst liquid material and the second liquid material to contact witheach other at the contact point (to provide the coalesced third materialat the contact point), wherein the (liquid) contact point is configuredat the second device opening or downstream thereof. Herein the term“above” as in the phrase “at a position above said second deviceopening” especially relates to a position being selected upstream of theliquid device opening (nozzle opening) such that a (spontaneous) flow ofthe first liquid (provided by gravity, inertia, or surface tension) overthe device face (nozzle tip) may contact the first liquid material withthe second liquid material at the second liquid device opening (toprovide the coalesced third material).

Hence, the indirect formation process especially comprises: providing asecond liquid jet comprising the second liquid material by a secondliquid providing device comprising a second device face and a seconddevice opening, wherein the second liquid jet is directed with a secondliquid jet direction, and providing the first liquid material to thesecond device face at a position upstream of the second device opening,and allowing the first liquid material and the second liquid material tocontact with each other at the contact point (to provide the coalescedthird material at the contact point), wherein the (liquid) contact pointis configured at the second device opening or downstream thereof.

Especially, allowing the first liquid material and the second liquidmaterial to contact each other at the contact point may compriseallowing the first liquid material to temporarily accumulating at thesecond device face and successively (flowing downwards (especiallybecause of gravity and)) contacting the second liquid material at the(first) contact point. Herein such embodiments of the process(especially wherein a first material is provided to a face andsuccessively contacts another material at a contact point) especiallyrelate to an “indirect contacting” formation process.

Herein the term “contact point” relates to a position where a (liquid)material contacts another (liquid) material. Especially, herein the term“(virtual) collision point” relates to a location where a liquid jet(potentially) contacts (or collides with) another liquid jet, especiallyin the gaseous atmosphere. The term “collision point” is especially usedin relation with in-flight collisions (in the in-flight formationprocess). The term “contact point” may be used in relation to in-flightcollisions, but also in relation to an indirect contacting via a face(see below).

Hence, in an aspect, the invention provides a production process(“process”) comprising an in-flight formation process, the in-flightformation process comprising: providing in a gas atmosphere (i) a firstliquid jet directed with a first jet direction to a (virtual) (first)collision point in said gas atmosphere, wherein the first liquid jetcomprises a first liquid material, and (ii) a second liquid jet directedwith a second jet direction to the (virtual) (first) collision point,wherein the second liquid jet comprises a second liquid material, toprovide a (coalesced) third material at the (virtual) (first) collisionpoint propagating in a third direction. Especially, the (first) contactpoint comprises the (virtual) (first) collision point.

Especially, in the production process, the first jet direction of thefirst liquid jet and the second jet direction of the second liquid jethave a mutual angle larger than 0° and equal to or smaller than 75°,especially equal to or smaller than 60°, such as equal to or larger than5°, such as equal to or larger than 10°, and equal to or smaller than45°. In embodiments the mutual angle is larger than 75°, such asselected in the range of 75−180°, especially in the range of 75°-90° orin the range of 90°-120°, such as substantially 90°. In yet furtherembodiments, the mutual angel is in the range of 120°-180°, such assubstantially 180°.

The production process comprises providing at least one of the firstliquid jet and second liquid jet as an uninterrupted liquid jet at said(first) collision point.

Especially, the process may comprise providing a liquid material throughan opening (or “orifice”) out of a liquid providing device, such as anozzle, comprising the opening, especially to provide the (respective)liquid jet comprising said liquid material. Such liquid providing devicemay comprise a device face (especially a face substantially notcontacting said liquid material). Especially, for providing a liquidjet, the liquid material is continuously, especially not intermittedly,provided through the opening.

Especially, in the production process described herein, the first liquidmaterial and the second liquid material have different materialproperties, such as different viscosities, different densities, and/ordifferent surface tensions, especially the first liquid material and thesecond liquid material have different surface tensions. In yet furtherembodiments, the first liquid material and the second liquid materialhave substantially the same surface tension.

Examples of a liquid material are a homogeneous liquid material and aheterogeneous liquid material, such as a suspension. A liquid materialmay comprise some gas or air, and may in embodiments comprise a foam. Aliquid jet especially comprises a liquid material. In yet furtherembodiments of the invention, the first liquid material and the secondliquid material have substantially the same material properties.

The first liquid material and the second liquid material especiallycoalesce at the (virtual) (first) collision point. Especially, the firstliquid material and the second liquid material merge or pull together(i.e. coalesce) when providing (the third jet comprising) the thirdmaterial (see further below). Especially, at a collision point,respective materials that collide at said point substantially do not(mutually) bounce, splash, atomize or e.g. provide a mist. Inembodiments, at least 50 vol. %, such as at least 70 vol. %, such as atleast 80 vol. %, such as at least 90 vol. % of the liquid materialsarriving at a collision point (such as the first liquid material and thesecond liquid material) propagate(s) as a jet (such as a third jet) ofthe (e.g. third) coalesced material.

Especially, (also) the jets comprising the respective materials areconfigured not to atomize before impact (at the collision point).Especially, said jets are not configured in a wind-induced break upregime. Hence, especially a gas Weber number of a gas surrounding theliquid jet is smaller than or equal to 0.2, see further below.

In another aspect, the invention provides a device (or apparatus),especially for (use in) such production process comprising a formationprocess, the device comprising: a first liquid container configured tocontain a first device liquid comprising a first device liquid material,in fluid connection with a first liquid providing device comprising afirst device opening; a second liquid container configured to contain asecond device liquid comprising a second device liquid material, influid connection with a second liquid providing device comprising asecond device opening; a first liquid transporter configured totransport the first device liquid from the first liquid container to thefirst liquid providing device and through the first device opening; asecond liquid transporter configured to transport the second deviceliquid from the second liquid container to the second liquid providingdevice and through the second device opening. Especially, at least oneof the first liquid providing device and the second liquid providingdevice is configured to provide the respective device liquid material asa liquid jet propagating in a direction. Especially the first liquidproviding device and the second liquid providing device are configuredfor providing the first device liquid and the second device liquidcontacting each other at a contact point.

Especially, the second liquid providing device comprises a second deviceface. Such device may be used for an in-flight formation process.Alternatively or additionally, such device may be used for an indirectcontacting formation process.

Hence, the invention provides a device (or apparatus) (especially for(use in) such production process comprising an in-flight formationprocess and/or an indirect contacting formation process), the devicecomprising: (i) a first liquid container configured to contain a firstdevice liquid comprising a first device liquid material, in fluidconnection with a first liquid providing device comprising a firstdevice opening; (ii) a second liquid container configured to contain asecond device liquid comprising a second device liquid material, influid connection with a second liquid providing device comprising asecond device opening; (iii) a first liquid transporter configured totransport the first device liquid from the first liquid container to thefirst liquid providing device and through the first device opening toprovide a first device liquid jet (comprising the first device liquid);(iv) a second liquid transporter configured to transport the seconddevice liquid from the second liquid container to the second liquidproviding device and through the second device opening to provide asecond device liquid jet (comprising the second device liquid).

Especially, the first device opening and the second device opening aredirected to a (virtual) (first) collision point in line of sight of bothdevice openings, wherein the device openings and the (virtual) (first)collision point define an angle larger than 0° and equal to or smallerthan 75°, especially equal to or smaller than 60°, such as equal to orlarger than 5°, such as equal to or larger than 10°, and equal to orsmaller than 45°. Especially, the contact point comprises the (virtual)(first) collision point and especially, the first device liquid and thesecond device liquid are provided to contact each other at the (virtual)collision point. In embodiments the device openings and the (virtual)collision point define an angle larger than 75°, such as selected in therange of 75−180°, especially in the range of 75°-90° or in the range of90°-120°, such as substantially 90°. In yet further embodiments, saidangle is in the range of 120°-180°, such as substantially 180°.

Especially, the first liquid providing device comprises the first liquiddevice. Likewise, especially any further liquid providing device,especially the second liquid providing device, may comprise any(respective) further liquid device, especially the second liquid device.

In embodiments, the first device opening is directed to the seconddevice face. The term “face” especially relates to a face (of a liquid(providing) device) remote from the liquid material (in the liquidproviding device and) provided by said liquid providing device.Especially the face substantially does not contact the liquid material(liquid jet) provided by said liquid device. Especially the face mayreceive the other liquid material and allow the other liquid material toflow towards the device opening, especially allowing to contact theliquid material (liquid jet) provided by said liquid providing device. Aface may comprise one or more faces, especially faces contacting eachother. A face may comprise a curved shape. Additionally or alternativelya face may comprise a straight shape or any other shape.

Especially, the second liquid providing device comprises a (second)nozzle, and especially the first device opening is directed to a face ofthe second nozzle (“second nozzle face”). In further embodiments, thefirst device opening is configured in physical contact with the seconddevice face. Especially the first device opening is configured inphysical contact with the second nozzle, especially the second nozzleface.

This production process (“process”) and/or the device allow a relativeeasy and quick production and/or processing of all kinds of materials,including synthetic or natural polymers, plastics, metals, glasses,biological materials that contain or do not contain cells, foams,suspensions, emulsions, solutions, melts, solvents, etc., in all kindsof shapes. With the process, complex 3-dimensional structures as well ascylinders including fibers, spheres, spheroids, and disk-like shapes maybe produced. Embodiments of the invention may be applied for additivemanufacturing applications.

Especially, a device liquid jet comprises a liquid jet. Both terms referto a liquid jet, but the first device liquid jet is not necessarily thefirst liquid jet, etc. Especially, the first device liquid jet,comprises the first liquid jet, and the second device liquid jetcomprises the second liquid jet, etc. However, the first device liquidjet not necessarily comprises the first liquid jet, nor does the seconddevice liquid jet necessarily comprises the second liquid jet, etc. Itis noted that the first liquid providing device of the device accordingto the invention may comprise the first liquid material or the secondliquid material, etc. The second liquid providing device may, e.g.,comprise the first liquid material if the first liquid providing devicecomprises the second liquid material, etc. The terms first, second,third and the like in the description and in the claims, are used fordistinguishing between similar elements and not necessarily fordescribing a sequential or chronological order. Analogously, also thefirst liquid device jet (of the device according to the invention) maycomprise the first liquid jet. Alternatively, the first liquid devicejet may comprise the second liquid jet (according to the process of theinvention), and vice versa. Hence, also the first liquid material (ofthe production process) may comprise the second liquid container of thedevice, etc. The first (device) liquid jet and the second (device)liquid jet are especially configured to provide the first liquidmaterial and the second liquid material at a mutual contact point.Especially, a first liquid material is provided by a first liquid jetprovided by a first liquid providing device.

In embodiments, a contact point comprises a collision point. Especiallya first (device) liquid jet and a second (device) liquid jet aredirected to a collision point, especially to combine, especially toprovide a (coalesced) third material at the collision point, andpropagating in a third (jet) direction. In other embodiments, especiallythe first (device) liquid jet is directed to the second device face,especially to contact the second material provided by the second(device) liquid jet (provided at a device opening), especially toprovide a (coalesced) third material, and propagating in a third (jet)direction.

Especially, a third jet (comprising the third (jet) direction) maycomprise the third material. Especially, at the collision point a thirdjet is provided of the coalesced third material (propagating in thethird direction). The “liquid device” especially refers to a deviceconfigured to provide a liquid. Likewise, the term “liquid providingdevice” especially refers to a device configured to provide a liquid.Especially, a “liquid device” comprises a “liquid providing device”.Especially a liquid providing device comprises a face and a deviceopening. A liquid providing device may comprise a nozzle comprising aface and a nozzle opening, such as an orifice. Hence, a device face maycomprise a nozzle face. Likewise, a device opening may comprise a nozzleopening (especially for providing a (device) liquid material).Especially, a device opening may comprise an orifice.

Herein the term “opening” such as in “nozzle opening” and “deviceopening” may also relate to more than one opening. Hence, a nozzle or aliquid (providing) device may comprise more than one opening. Inembodiments, the (liquid) providing device comprises at least two(device) openings, especially arranged next to each other, such as in analigned array, or in any other configuration. In a further embodiment,the (device) openings are arranged coaxially. In an embodiment thenozzle comprises two coaxially arranged (device) openings. Inembodiments, at least one of the liquid providing devices comprises anozzle comprising two coaxially arranged (device) openings. Hence, atleast one of the liquid providing devices (such as the first, the secondor any optional further liquid providing device) may comprise twocoaxially arranged device openings. In further embodiments all liquidproviding devices comprise a single device opening.

Hence, a liquid jet (especially provided by a liquid providing devicecomprising two coaxially arranged device openings) may comprise twoliquid materials. In an embodiment, at least one of the first liquidjet, the second liquid jet and the optional forth or further liquid jetcomprises two respective (especially first and/or second and/orforth/further) liquid materials. A jet comprising two liquid materialsmay be directed to a collision point and collide with another jet toprovide the coalesced material at a collision point.

In an embodiment (comprising a liquid providing device comprisingcoaxially arranged device openings), further, the second liquid materialmay be provided through the inner opening and the first liquid materialmay be provided through the outer opening, and especially the firstliquid material and the second liquid material may contact with eachother at a contact point (especially at the inner opening or downstreamthereof), providing the coalesced third material. In a furtherembodiment comprising a nozzle with two axially arranged openings,especially a center opening and an outer opening surrounding the centeropening, a liquid material is provided through the inner opening and agas may be provided through the outer opening. In yet furtherembodiments, a coaxially arranged device opening may be used to provideone or more of the first or second liquid material and another fluid,which is different from first or second liquid material, and optionallyat least part of the other fluid, may coalesce with the second or firstliquid material. The other fluid may be a gas or liquid, especially aliquid. When the other fluid is a liquid, at least part thereof may alsocoalesce with the second or first liquid.

The second liquid jet may be provided by a second liquid providingdevice (comprising a second device face, etc.). Similarly, the firstliquid jet may be provided by a first liquid providing device, etc. Inembodiments, the device according to the invention may be configured toprovide a second device liquid jet (comprising the second device liquidmaterial) through the second device opening, wherein the second liquidproviding device comprises a second device face and said second deviceopening, wherein the first device opening is directed to the seconddevice face to provide the first device liquid to the second deviceface, especially wherein the first device opening is configured inphysical contact with the second device face. Hence, in embodiments, thesecond liquid jet is provided by a second nozzle and the first liquidjet is directed towards a second nozzle and may impact the second nozzleface. Especially, in such embodiments, the first liquid materialprovided to the second device face (second nozzle face) may flow(especially as a result of gravitational forces) from the second deviceface (second nozzle face) towards the second liquid material (providedat the second device opening or nozzle opening). In such embodiments,the first liquid material may contact the second liquid material at thesecond device opening (second nozzle opening) or (just) downstream ofthe second device opening. In such embodiment, the contact point may beconfigured at the second device opening or downstream thereof.

Especially, the second liquid jet may comprises the contact point at alocation (very) close to the second device opening (especially thesecond nozzle opening). Especially, in such embodiments, the firstliquid material may contact the second liquid jet at substantially thesame moment the second liquid jet is provided (formed) (at the secondliquid opening). Yet in further embodiments, a contact point comprises acollision point.

Hence the elements “contacting a first liquid material and a secondliquid material with each other at a contact point in a gas atmosphere”“to provide at the contact point a (coalesced) third material” asdescribed herein may relate to directing a first liquid material (afirst liquid jet) and a second liquid material (a second liquid jet) toa (virtual) collision point (to provide a collision) wherein a thirdmaterial is provided at that collision point especially to provide thethird material (propagating in a third direction) at said contact point.Alternatively, or additionally (if e.g. the formation process comprisesmore than one formation process, see below), the elements may relate toproviding (a first liquid jet comprising) a first liquid material to (aface of) a (second) liquid providing device (such as a nozzle) providinga second liquid, and allowing the first liquid material to contact thesecond liquid material (the second liquid jet) at the contact pointconfigured at the second device opening or downstream thereof,especially to provide the third material (propagating in a thirddirection) at said contact point. Especially the second jet directionmay be configured to especially provide the third direction.

The liquid materials may contact each other at a contact point,especially at a collision point. It will be understood by a personskilled in the art that a “contact point”, or a “collision point” mayrelate to a (small) volume wherein the liquid materials contact eachother (rather than to a discrete single point). Such a volume may beaffected by the flux (or flow, especially an average quantity in adetermined time) of the liquid materials. In embodiments, said volumemay e.g. comprise at least 1 picoliter, such as in the range of 1picoliter-1 ml, especially at least 1 microliter. In furtherembodiments, said volume may comprise 1-100 ml.

In embodiments, the device comprises: (i) a first liquid containerconfigured to contain a first device liquid comprising a first deviceliquid material, in fluid connection with a first liquid providingdevice comprising a first device opening; (ii) a second liquid containerconfigured to contain a second device liquid comprising a second deviceliquid material, in fluid connection with a second liquid providingdevice comprising a second device opening and a second device face;(iii) a first liquid transporter configured to transport the firstdevice liquid from the first liquid container to the first liquidproviding device and through the first device opening; (iv) a secondliquid transporter configured to transport the second device liquid fromthe second liquid container to the second liquid providing device andthrough the second device opening to provide a second device liquid jet,especially propagating in a second jet direction, especially wherein thefirst device opening is directed to the second device face (to providethe first device liquid to the second device face), and/or wherein thefirst device opening is configured in physical contact with the seconddevice face to provide the first device liquid to the second deviceface.

In such embodiments the first (device) liquid is provided to the seconddevice face. In embodiments, a material of the second device face may beselected to provide (a degree of) wetting of the second device face(with the first liquid material). The second (device) liquid jet maydrag the first (device) liquid material along when provided through thesecond device opening. Especially, such embodiments may provide a lesscomplex alternative to coaxial flow devices (e.g. used forspinning/spraying) known in the art. Such embodiment may provide a jetcomprising a smaller diameter (perpendicular to the longitudinal axis ofthe jet), relative to a coaxial flow device. Known, coaxial flow deviceson the market may not be able to provide a jet with a diameter smallerthan 100 μm. However, in embodiments, the device according to theinvention may provide a jet comprising a diameter smaller than 100 μm,such as equal to 10 μm.

In in-gas microfluidics (IAMF), at least two liquid materials,especially having different physical characteristics, especially areejected and collide (in-flight) in a gaseous atmosphere. In otherembodiments, said at least two liquid materials contact each other at acontact point especially at a device opening providing one of the liquidmaterials or downstream of said device opening. Especially, the liquidmaterials contact each other. Subsequently the materials combine,especially coalesce, to form a third material. By selecting the surfacetension of the liquid materials differently coalesced material may beformed wherein a part of the liquid may encapsulate the remainder of theliquid.

Herein the terms “jet” and “stream” as in “liquid jet” and “liquidstream” are used interchangeably. Especially, a (liquid) jet comprises a(liquid) stream. The terms especially refer to a physical identity thatis understood by the person skilled in the art and that may represent anintact non-broken, uninterrupted, and continuous stream of liquid (an“uninterrupted jet”) as well as a broken, interrupted jet comprising aflow of liquid droplets, (all) traveling in the same (jet) direction,especially parallel to a longitudinal axis of the jet. In a jet, thecontent of the jet is continuously refreshed as liquid is provided at anupstream side of the jet and discarded (or collected) at a downstreamside of the jet. A length of a jet may be defined as a distance betweenthe upstream side of the jet and the downstream side of the jet. Hence,a jet may comprise an upstream side and a downstream side. Especially, ajet is generated at the upstream side, especially at the origin of thejet, e.g. at a device opening, such as an opening of a nozzle.Alternatively or additionally an origin of the jet may also comprise acontact point. Especially, the origin of the third jet comprises the(first) contact point. In a jet the (liquid) material especially flowsfrom an upstream location to a downstream location. A jet, especiallydoes not fan-out or disperse over the length of the jet. Locally, across section of a jet (perpendicular to the longitudinal axis of thejet) may vary in a modulated jet or e.g. a droplet train. However,especially a mean (or maximal local) cross section of the jetsubstantially does not change over the length of the jet. Especially, aratio of the mean (or maximal local) cross section at the downstreamside to the mean (or maximal local) cross section at the upstream sideis in the range of 0.1-10, especially 0.25-4, such as 0.5-2, like about1.

A jet may contact a surface, another liquid material, or any otherdisturbing material at any location between the origin of the jet andthe (potential) downstream side of the jet. Especially, the potentialdownstream side refers to the downstream side of the same jet at themoment it does not contact any disturbing material, and thus may flowfreely. In embodiments, the jet may contact another material at aposition very close to the origin of the jet. In embodiments of theinvention a jet may be provided and substantially at the same moment thejet may contact another material at a location of the jet (at a contactpoint being substantially coinciding with the origin of the jet). Suchjet may comprise a length (a distance between the origin of the jet andsaid location being substantially zero (however, especially beingnon-equally to zero). Hence, herein the term (liquid) “jet” may refer toa jet (or stream) with a length being substantially zero. In otherembodiments the term (liquid) “jet” may refer to a jet having a lengththat is substantially larger than zero. Especially, in embodimentswherein a (first) liquid material is provided at a (second) device faceto contact a second liquid material provided through the device opening,the length of the (second) liquid jet may be substantially zero.Optionally in such embodiment also a length of a first liquid jetcomprising the first liquid material may be substantially zero (e.g.wherein a first nozzle opening is applied to provide the first jet, andthe first nozzle opening substantially contacts the second device face).

The term “a (liquid) jet” may refer to a single (liquid) jet. The termmay also refer to a plurality of (liquid) jets. Especially, the term “asecond liquid jet” may refer to a single second liquid jet. Inembodiments, the term may also refer to a plurality of second liquidjets. Especially a plurality of jets (and the like) may comprise atleast 2 jets, such as 2-1000 jets, especially 2-100 jets, even moreespecially 2-25 jets, such as 2-10 jets (and the like). Likewise, theterms “second liquid device opening” and the second liquid transporter”and the like, may also refer to a plurality of second liquid deviceopenings and a plurality of second liquid transporters, etc. Each of thesecond liquid jets (of the plurality of liquid jets) may be directed tothe (same) contact point, especially, the (same) virtual collisionpoint. Especially, the second liquid jets of said plurality of liquidjets may (all) have substantially the same mutual angle with the firstliquid jet. Hence, in embodiments a first liquid jet (material) and aplurality of second liquid jets (comprising the second liquid material)may provide the (coalesced) third material (at the virtual collisionpoint) propagating in the third direction (see also below). Especially,in such embodiments, the plurality of second liquid jets may beconfigured to control the third direction. For instance, a second liquidjet comprising two second liquid jets may allow to direct the thirdmaterial in a two dimensional direction. A second liquid jet comprisingat least three second liquid jets may allow to direct the third material(even) in a three dimensional direction (see also below).

A (liquid) jet may be characterized comprising a stable, uninterrupted,or continuous liquid jet that remains continuous (intact) until the jetcollides (with another jet, or e.g. a surface). A jet may also becharacterized as an unstable and being broken up (especially indroplets), providing a liquid jet comprising only droplets, especiallymonodisperse droplets (see below). It is noted that a jet, especially anunstable jet, may be characterized by three parts: (a) a first partlocated most closely to the upstream side of the jet may show a straightintact liquid jet, wherein a width perpendicular to the longitudinalaxis of the jet is substantially equal over said first part of the jet,(b) a last part, most remote from the upstream side, comprising onlyseparated droplets, and (c) an intermediate part that connects the firstpart to the second part and comprising a distinguishable instabilitythat may be observed from the width of the jet that changes, especiallythe width may repeatedly increase and decrease in the longitudinaldirection of the jet. In the downstream direction especially theinstability in the intermediate part may increase until the jetbreaks-up. Hence, an instable or broken up jet, especially is providedas a continuous, uninterrupted jet at the origin of the jet and mayfurther downstream of the origin break up and form an interrupted (orintermitted) jet. Especially, a location of the intermediate part, mostremote from the origin of the jet, may be referred to herein as thebreaking point, wherein a shortest length of a line connecting theorigin of the jet and the breaking point is defined as L_(B) herein. Inembodiments of the production process at least one liquid jet isimpacted by another liquid jet at a location in the intermediate part ofthe jet. In other embodiments at least one jet is impacted by anotherjet at a location in the first part of the jet. In yet otherembodiments, at least one jet is impacted by another jet at a locationin the third part of the jet (see also below). In yet other embodimentsa jet first impacts with a surface and successively contacts anotherjet. Especially in such embodiment, the other jet may comprise an intactjet or a broken jet (e.g., comprising droplets).

The invention provides the production process comprising at least twoliquid jets, such as two liquid jets, three liquid jets, four liquidjet, etc., especially providing a (coalesced) material that mayespecially be received, e.g. in a container, in a mold, at a substrateor in a receiving liquid. Especially said (coalesced) material isprovided by contacting a liquid material with at least one furtherliquid material.

The invention is now first explained based on an embodiment of theproduction process comprising two liquid jets, see also e.g. thetop-side of FIG. 1 (FIG. 1 depicts a process comprising three jets,however the top side is representative for a process comprising twoliquid jets), wherein one liquid jet is an uninterrupted or continuousjet at the (first) collision point (also described herein as “at themoment of impact” or “at the location of impact”), and the other liquidjet comprises only droplets at the moment of impact. Especially in theformer embodiment, the collision point comprises the contact point. Theinvention is also explained by another embodiment comprising a first jetprovided at a face of a liquid (providing) device providing the secondjet, see FIG. 8.

Herein this combination of an uninterrupted (also referred herein as“intact”) jet impacting a jet of droplets is also referred to as a“drop-jet” mode. Herein, also the term “droplet train” and “drop train”is used for a liquid jet comprising only droplets. Hence, in the dropjet mode, a droplet train impacts onto an intact liquid jet (or viceversa). In embodiments of the process the first liquid jet is directedfrom a first liquid providing device (nozzle) towards a (second) liquidproviding device (nozzle) providing the second liquid jet, and the firstliquid material contacts the second liquid material (substantially) atthe (second) device opening (nozzle opening) or downstream from thesecond device opening. Herein such embodiment may also be referred to as(comprising) a “jet-nozzle” mode or a “nozzle-nozzle”mode. The processrelated to such mode, may also be referred to as “indirect contacting”.Especially, wherein the “jet-nozzle” mode relates to an embodimentwherein a (first) jet is directed to a (second) device face (a secondnozzle face) (e.g., as depicted in FIG. 8), especially wherein the(first) liquid jet impacts at the (second) device face. Especially a“nozzle-nozzle” mode relates to a configuration wherein a first liquidproviding device (nozzle) providing said first liquid material isconfigured in physical contact with the second device face, especially asecond nozzle face. Especially a jet-nozzle mode comprises anozzle-nozzle mode. Especially a device opening of the (first) liquiddevice may physically contact the (second) device face (or nozzle).

To provide a jet to break-up more easily, in embodiments, said jet maybe modulated. Additionally or alternatively, a jet may break-up whencontacting a face, such as a face of a nozzle. Especially, in ajet-nozzle mode and/or a nozzle-nozzle mode a jet may break-up whencontacting the nozzle (face). Especially, a jet-nozzle mode or anozzle-nozzle mode may comprise a drop-drop mode, or a jet-drop mode ora jet-jet mode (see below).

A modulation may be provided on to the jet by a liquid device (such as(a combination of) (a) liquid providing device(s) (according to theinvention) generating the jet(s). Especially, the device may comprise a(modulating) actuator suitable for providing the modulation (e.g. byproviding vibrations to the liquid device). Specific (modulating)actuators may include, but are not limited to (1) an actuation deviceintegrated with the nozzle as e.g. used in piezo-electric inkjetprinters, (2) a piezo-electric element connected to the nozzle or to aliquid transporter, or (3) an actuation device as used in earphones orearplugs. In the latter two cases, the connection of the (modulating)actuator can be provided e.g. by pressing the nozzle or liquid connectoronto the actuation device (or vice versa), or gluing by adhesive tape ofsolidifying glue. In embodiments, at least one liquid device comprisesan (modulating) actuator to provide a modulated jet. In embodiments, anozzle is actuated, and especially the (modulating) actuator comprises apiezo-electric element. In other embodiments the (modulating) actuatorcomprises a vibrating element that directly induces a fluctuatingpressure onto the liquid material. Modulating a liquid jet mayespecially provide breaking up of the jet in small droplets, especiallyhaving a diameter selected in the range 1-10, especially 1-5, such as1-3, even more especially 1-2 times as large as a diameter of the liquiddevice opening providing the respective liquid jet. Such broken up jetmay comprise a continuous flow of small droplets, especially wherein adistance between subsequent droplets is substantially constant.

In further embodiments, the (modulating) actuator comprises an elementconfigured to vibrate. Especially, one or more of the first liquid(providing) device and the second liquid (providing) device comprises a(modulating) actuator comprising an element configured to vibrate(“vibrating element”). Herein, a (modulating) actuator may also relateto more than one (different) (modulating) actuators. In embodiments,each liquid providing device comprises a (modulating) actuator. Infurther embodiments one or more liquid providing devices (together)comprise one (or more) (modulating) actuator(s). In yet furtherembodiments, the liquid providing devices are configured at a base,especially wherein the base comprises a (modulating) actuator.Especially a vibrating element is arranged to provide a vibration to aliquid (providing) devices, especially to a nozzle of the liquid(providing) devices, and especially to a liquid jet provided by thatnozzle.

An element to vibrate (vibrating element) may be configured to vibrateat a frequency (of vibration). Especially, in embodiments of the process(see also below), a vibration may (also) be selected to comprise saidfrequency. Such frequency may, e.g., be selected in the range of asingle hertz. Alternatively or additionally, the frequency may beselected in the kilohertz range. Yet, the frequency may further beselected in the megahertz range. Especially, the element (configured tovibrate) may be configured to vibrate at a frequency selected in therange of 0.1 Hz-100 MHz, especially 1 Hz-100 MHz, such as in the rangeof 1 Hz-1 MHz, especially in the range of 100 Hz-1 MHz, even moreespecially in the range of 100 Hz-100 kHz. In further embodiments, thefrequency is selected in the range of 1 kHz-1 MHz, such as 1 kHz-100kHz. Hence, a liquid providing device according to the invention maycomprise an actuator, especially to provide a vibration (having afrequency) to a liquid nozzle. In embodiments of the process thefrequency may (also) be selected in the above given ranges. Hence, theprocess according to the invention may comprise vibrating one or more ofthe liquid devices.

Especially, a nozzle may be actuated to affect the breakup of a liquidjet into a droplet train. Especially, monodisperse droplets may begenerated by controlled breakup of a liquid jet ejected from a nozzle.Especially, a monodisperse droplet train may be directed to an intactliquid jet ejected from another nozzle. When the droplet train impactsonto the intact liquid jet this may provide a coalesced third materialpropagating in a third direction. A jet may also be directed to a faceof a liquid device providing a droplet train, providing a coalescedthird material propagating in a third direction. In embodiments, it mayresult in a compound monodisperse droplet train flowing downwards.Especially, the term “monodisperse” droplets relates to a monodispersedsize distribution of droplets, wherein the standard deviation is lessthan 30% (of the average size), especially less than 8% (of the averagesize)

Hence, in embodiments, the production process (further) comprisesmodulating one of the first liquid jet and the second liquid jet forproviding one of the first liquid jet and the second liquid jet asinterrupted liquid jet at said collision point. In further embodiments,the production process (further) comprises modulating one of the firstliquid jet and the second liquid jet (especially the second liquid jet)for providing one of the first liquid jet and the second liquid jet(especially the second liquid jet) as interrupted liquid jet at saidcontact point. Especially, the device described herein comprises one ormore (modulating) actuators configured to provide one or more of amodulated first device liquid jet and second device liquid jet. Inembodiments, the device may comprise one (modulating) actuatorconfigured to modulate the first device liquid jet and the second deviceliquid jet. However, in specific embodiments the production processcomprises providing at least one of the first liquid jet and secondliquid jet as uninterrupted liquid jet at said collision point and/orcontact point. Hence, for this jet there may be no modulation or amodulation that does not lead to a break-up of the jet at a locationupstream of the collision point. Especially, the (modulating) actuatormay be configured to provide a vibration to a nozzle. For providing acontinuous (modulated) jet, the vibration may be continuous, especiallycomprising a steady (especially continuous and substantiallynon-changing) frequency. Hence, in further embodiments, the productionprocess (further) comprises providing a vibration to a liquid jet,especially for providing the liquid jet as a modulated liquid jet (seealso below). In embodiments, a vibration is provided to the first liquidjet (providing a modulating first liquid jet). In further embodiments, avibration is provided to the second liquid jet (providing a modulatingsecond liquid jet). Yet, in further embodiments, a vibration is providedto a further liquid (providing) jet (and providing a modulating furtherliquid jet). In further embodiments, the production process comprisesproviding a vibration to one of the first liquid jet and the secondliquid jet (especially the second liquid jet) for providing one of thefirst liquid jet and the second liquid jet (especially the second liquidjet) (especially the respective liquid jet, especially provided with thevibration) as interrupted liquid jet at said contact point. Herein,providing a vibration (or modulation) to a liquid jet, may especiallyrelate to providing a vibration to a liquid providing device (providingthe liquid jet), especially to a nozzle thereof.

Especially, the two liquid materials coalesce, and one liquid phase(optionally) encapsulates (and immobilizes) another liquid phase (i.e.,the remainder of the liquid), and especially at least part of theprovided third material may solidify.

It was experimentally found that coalescence, encapsulation, andsolidification dynamics that occur (in-flight), in the gaseousatmosphere seem to play an important role in IAMF (see also FIG. 2).First, the droplet impacts onto the jet. Especially, impact may resultin coalescence, i.e. bouncing preferably is prevented. Furthermore,production of spherical particles especially may require that thedroplet substantially maintains its spherical shape during impact.Experimentally (see experimental section) it was found that bothconditions may be met if the impact Weber number We_(impact)=ρV²_(impact)D₁/σ₁<50, preferably <10, with ρ the density, D₁ the dropletdiameter, and σ₁ the surface tension of (the liquid in) the droplet,wherein the impact velocity V_(impact)=V_(ej) sin Θ depends on theimpact angle Θ and the ejection velocity (the velocity at the opening ofthe liquid device) V_(ej) of the jet providing the droplet train.Especially, for a jet-nozzle and/or a nozzle-nozzle mode said conditionmay be met under most practical conditions, especially since V_(impact)may be substantially. For instance, in embodiments the impact velocitymay be selected from the range of 0.2-500 m/s, such as 0.2-50 m/s, like0.2-30 m/s. Yet, in other embodiments, the impact velocity is may be inthe range of 0.05-0.2 m/s.

After impact, coalescence of part of a liquid jet, especially part ofthe intact fluid jet, and part of another liquid jet, especially adroplet of a droplet train, may be provided.

For providing a liquid jet, especially the liquid Weber number We₁ isselected to be equal to or larger than 1. The liquid Weber number, We₁being defined as ρ₁V²D/σ₁, with ρ₁, V, σ₁ being the density, velocityand surface tension of the liquid respectively. D relates to acharacteristic dimension of the jet, especially the diameter of the jet.Yet, in embodiments, the Weber number as well as the diameter D may berelated to a diameter of a droplet in the liquid jet. The liquid jet maybe provided in the Rayleigh breakup regime, especially to providedroplet formation by Rayleigh breakup.

The upper liquid Weber number (velocity limit) may be bounded bywind-induced breakup, which occurs for gas Weber numbersWe_(g)=ρ_(g)/ρ_(l)·We_(l)>0.2, with ρ_(g) the density of the gas. TheRayleigh breakup regime especially relates to a jet provided in a gas,comprising a (liquid) weber number equal to or larger than 1, whereinthe gas weber number is equal to or smaller than 0.2. When the liquidvelocity (in the liquid jet) further increases, a velocity of the jetrelative to a velocity of the surrounding gas may no longer beneglected. Aerodynamic effects may accelerate a breakup process and ashortening of the length between the nozzle exit and a location ofdroplet pinch-off may be observed. Especially a transition from theRayleigh breakup regime to a first wind-induced breakup regime may occurwhen the inertia force of the surrounding atmosphere (gas) reaches asignificant fraction of the surface tension force, especially atWe_(g)>0.2. Hence, especially, the gas Weber number is selected to beequal to or less than 0.2 to prevent a wind-induced break-up of theliquid jet. Hence, for providing a continuous liquid jet or aninterrupted liquid jet, especially, the liquid Weber number is selectedto be smaller than or equal to 0.2*ρ_(l)ρ_(g). Especially, the liquidWeber number is selected to be larger than or equal to 1, especiallylarger than or equal to 3, such as larger than or equal to 4, forproviding a continuous liquid jet The production process of theinvention essentially comprises coalescing a liquid material (of aliquid jet) with a further liquid material (of further liquid jet).Especially, said liquid materials substantially completely coalesce.Especially, the production process does not comprise wind-inducedbreakup. The production process of the invention especially (also) doesnot comprise atomization of a liquid jet. Wind-induced breakup butespecially atomization may disable a substantially complete coalesce.

Especially, in an indirect contacting formation process (especially in ajet-nozzle mode), contact of a first liquid material with a secondliquid material, especially a droplet of a droplet train (comprising thesecond liquid material (jet), may result in coalescence of the secondliquid material and the first liquid material. The type of coalescencemay depend on the material properties of the combined liquid materialsas is understood by the person skilled in the art. Coalescence, may,e.g., occur as a segmenting (segmented) coalescence (especially whereina droplet—of a droplet train—collides and sticks to a jet andsuccessively almost directly the jet breaks up into segments) or aclinging coalescence (especially, a collision in which a drop or a jethits and clings to the (other) jet and vice versa providing an intactjet (that eventually may break up). Encapsulation of liquid by anotherliquid may be affected by the difference in the surface tension (of theliquid material) of the two liquids, especially of the liquid materialsof the liquid jets (the first liquid material and the second liquidmaterial). Especially, when the surface tension of a first liquid(especially comprised in the liquid material of the intact liquid jet)is lower than the surface tension of another liquid (especiallycomprised in the liquid material of a droplet train), the liquid of thefirst liquid may encapsulate the other liquid. Especially, when thesurface tension of a first liquid material accumulated at a nozzle faceand flowing down from said nozzle is lower than the surface tension ofanother liquid material of a jet provided by said nozzle, the firstliquid material may encapsulate the other liquid (at the contact point).As a result, a thin film of the low surface-tension liquid may be“pulled” around a higher surface-tension liquid and may immobilize thehigher surface tension liquid. Pulling of this thin film of the lowersurface tension liquid around the higher surface tension liquid may bethe result of a Marangoni flow (driven by a surface tension gradient).This mechanism may allow for (rapid) (in-air) encapsulation of bothmiscible and immiscible liquids, while limiting droplet deformation.Alternatively or additionally, the mechanism may allow encapsulationinitiated by surface tension differences induced by surfactants in pureliquids and/or mixtures. Especially, the surface tension of the twoliquid materials colliding (at the collision point) may be selected tobe different.

Especially, the surface tension of the two liquid materials contacting(at the contact point) may be selected to be different. A (largest)ratio of the surface tensions of the different liquid materials is atleast 1.005, such as at least 1.01, especially at least 1.05. Especiallythis ratio is at maximum 10, especially at maximum 7. Hence inembodiments a ratio of the different surface tensions is at least 1.05and not more than 7. Alternatively to selecting the surface tension ofthe liquid material in the (uninterrupted) jet lower than the surfacetension in the liquid material of the droplet train, the surface tensionof the liquid material in the intact jet may be selected to be higherthan the surface tension of the liquid material in the droplet train.Especially, in such an embodiment, the liquid comprised in the droplettrain may encapsulate the liquid comprised by the (uninterrupted) jet.

Encapsulation of a liquid by another liquid may also be affected by theviscosity of a liquid and the contact between the different liquidmaterials. During experiments, it was noticed that it may beadvantageous using a jet-nozzle (including a nozzle-nozzle) mode (anindirect contacting formation process) for encapsulation of a liquidmaterial. Especially when contacting the other liquid material, theliquid material accumulated at the nozzle (and successively flowing tothe opening of the nozzle) may substantially completely encircle theother liquid material at the contact point in such embodiments. Thenozzle may break-up the liquid jet when the liquid impacts the nozzle.Especially, the liquid material may accumulate around (/about) thenozzle, and especially after flowing to the nozzle opening the liquidmaterial may encircle the other liquid material. Hence, in suchembodiments, especially the process conditions and hardware conditionmay affect the encapsulation process. Especially, in such embodiment,especially a high viscous liquid material may more advantageouslyencapsulate another liquid material. In such embodiments for instancealso the properties of the liquid device face may affect the process. Inembodiments, e.g. the nozzle face (liquid providing device face)comprises hydrophilic properties (e.g. a hydrophilic coating). In otherembodiments, the nozzle face (device face) comprises hydrophobicproperties (e.g. a hydrophobic coating). Especially, in such formerembodiments an aqueous first liquid material may advantageouslyencapsulate a second liquid material (provided through the deviceopening of the device) because it may accumulate all over the nozzle(device face). Especially, in the latter embodiments, a hydrophobicliquid material will advantageously spread around (about) the nozzle(device face), whereas an aqueous liquid material may accumulate only atone side of the nozzle (device face). The indirect contacting formationprocess may advantageously be applied for high viscosity liquidmaterials, such as for a viscosity equal to or larger than 100 mPa·s,such as equal to or larger than 1 Pas. The indirect contacting formationprocess may especially be applied if a Marangoni flow may be hindered orhardly is present. Alternatively, an in-flight formation processcomprising a plurality of second jets may be applied if a Marangoni flowmay be hindered or be hardly present (see also below). Especially, aMarangoni flow may be substantially absent for liquid materialscomprising a high viscosity.

In embodiments, the surface tension of the two liquid materials may alsobe selected to be substantially equal to provide the (coalesced) thirdmaterial. Especially, this last (coalesced) third material may comprisea homogeneous mixture of the first and second material. The thirdmaterial may comprise homogeneously distributed first and secondmaterial, especially comprising an irregular shape, and especially notbeing monodisperse. In other embodiments, the first and second materialsdo not mix. Especially in such embodiment, the third material maycomprise a heterogeneously distributed first and second material,especially comprising two segregated regions, for instance providing a“janus” particle (see further below). Hence a coalesced material mayalso comprise a heterogeneous material or a material comprisingsegregated regions.

Finally, at least part of the coalesced third material, such as a formedcompound droplet, may solidify. Solidification of droplets may enablethe production of particles. Especially, the inner and outer liquids canbe selected such that one or both of the inner and outer liquidsolidifies, for example by gelation, precipitation, or freezing, etc. Inembodiments, especially one or more of the first liquid material and thesecond liquid material are solidifiable. In other embodiments the firstliquid material and the second liquid material are not solidifiable.

Depending on the required time scales for these steps, typically the(in-flight) formation process may take less than a few seconds, such asless than a second, especially 10-500 ms. Subsequently, the coalescedthird material may be collected, e.g., in a collector, in a bath, or(deposited) onto a solid surface, or received in any other type ofreceptor element. The term “bath” especially relates to depositingand/or receiving and/or collecting the coalesced (third) material and/orproduct of the process (see below) in a liquid (in the bath). A bathespecially comprises a liquid. Hence, especially a distance between thecontact point and the receptor element may be configured to provide therequired time scale (see below).

Additionally or alternatively, using two stable, uninterrupted liquidjets, the production process may comprise a “jet-jet mode”, wherein bothjets are intact when they impact on each other. Hence, in otherembodiments, the production process comprises providing both the firstliquid jet and second liquid jet as uninterrupted liquid jets at saidcollision point. In embodiments (comprising a jet-nozzle mode ornozzle-nozzle mode) the jet directed to a face of a liquid providingdevice is not an intact jet any more when (the liquid material providedby said jet) contacting (contacts) the other jet (provided by saidliquid providing device). However, especially the liquid materialprovided by the former jet may still provide a continuous flow of saidmaterial towards the contact point. Especially, also such mode (whereina first intact jet is provided to a face of a liquid providing deviceand a second intact jet is provided by said device opening) relates to ajet-jet mode. In further embodiments, the production process comprisesproviding both the first liquid jet and second liquid jet asuninterrupted liquid jets. Alternatively, the first liquid may flow fromthe liquid device (face) in a continuous flow and especially envelop(see also above) the second uninterrupted jet. In further embodiments,the first liquid device opening is configured (coaxially) around thesecond device opening, especially in a nozzle comprising two coaxiallyarranged openings (see also above). Such embodiments enable to spinfibers, by solidifying one of the liquids prior to breakup of the mergedjet. Especially such mode may provide fibrous (core-shell) material.Hence in embodiments, one of the liquid providing devices is configuredto provide an uninterrupted (intact) (device) liquid jet at a locationup-stream of the collision point up to the collision point for providingthe third material, especially wherein the third material comprisesfibrous material. In further embodiments, a nozzle-nozzle and/or ajet-nozzle mode may provide the third material comprising fibrousmaterial.

Using two jets, the production process may in an aspect also comprise a“drop-drop mode”, wherein both jets comprise a droplet train, and the(droplets of the) two droplet trains impact on each other. Suchdrop-drop mode may e.g. advantageously be applied to sort out dropletsbefore impact. For instance deviating (e.g. in size or composition)droplets may be redirected (such as by air or electromagnetically)upstream of the collision point, and especially to prevent them fromending up in the (coalesced) third material.

Especially in the drop-jet mode, a shortest length of a line connectingthe origin of the liquid jet (the upstream side of the liquid jet)comprising the drop train (the modulated liquid jet) and collision pointis larger than LB. In embodiments comprising the jet-jet mode, bothliquid jets may not be modulated. In other embodiments, comprising thejet-jet mode, one of the liquid jets may be modulated, wherein the otherliquid jet may collide in said first part of the liquid jet.

Alternatively, the collision point may also be configured furtherdownstream, wherein the modulation in one of the liquid jets has induceda (regularly) changing width of the liquid jet in the longitudinaldirection. Especially, the collision point may be configured in theintermediate part of the liquid jet.

Hence in further embodiments, the production process comprisesmodulating one of the first liquid jet and the second liquid jet forproviding one of the first liquid jet and the second liquid jet asuninterrupted liquid jet having a variable width (over a certain lengthof the jet) in a direction perpendicular to the respective jet directionat said collision point. In further embodiments, the production processcomprises providing a vibration to one of the first liquid jet and thesecond liquid jet, to provide one of the first liquid jet and the secondliquid jet (i.e. the respective liquid jet being provided with thevibration) as uninterrupted liquid jet having a variable width (over acertain length of the jet) in a direction perpendicular to therespective jet direction at said collision point. Especially, avibration is provided by means of a (modulating) actuator comprising avibrating element configured to vibrate at a frequency described herein,especially selected from the range of 1 Hz-1 MHz, especially 100 Hz-1MHz. An actuator (comprising the vibrating element) may be comprised byone or more of a first liquid providing device providing the firstliquid jet and a second liquid providing device providing the secondliquid jet.

Embodiments of the device, especially of a liquid providing device, maycomprise the (modulating) actuator, especially the (modulating) actuatorcomprising the element configured to vibrate to provide one of more ofsaid (modulated) first (device) liquid jet and second (device) liquidjet with the respective (device) jet having a variable width in adirection perpendicular to a respective (device) jet direction.Especially, in such embodiments the device is configured to provide oneof more of said modulated first (device) liquid jet and second (device)liquid jet with the respective jet breaking into (liquid) subunits aftera breaking length (LB) determined from the respective device opening,wherein the breaking length (LB) is equal to or shorter than a distancefrom the respective device opening to the virtual collision point.Hence, a modulated jet may have a variable width in a directionperpendicular to its jet direction. Especially, said width is largerthan 0 at a (especially all) location(s) between the origin of the jetand the breaking length. Especially said with is non-zero at the originof the jet. Essentially, said width may include 0 at a locationdownstream from the breaking length. In further embodiments, thedistance between the collision point and the device opening may bearranged to be smaller than the (optional) breaking length of the jetprovided by the respective device opening. In such embodiment, theinstability (modulation) of the respective liquid jet may (aftercollision with a second liquid jet and together providing a third liquidjet of coalesced material) be transposed to the third liquid material.Successively, the third liquid jet may break into subunits (droplets).

Alternatively, the production process and the device may comprise atleast one further (such as a fourth) liquid (device) jet and optionallyliquid providing device, next to two (device) liquid jets and optionallytwo liquid providing devices. A further liquid jet (or liquid device jetprovided by a liquid providing device), for instance is comprised inembodiments, wherein the further (device) liquid jet is directed to afurther contact point or further collision point, and wherein thefurther collision point is located at one of the first (device) liquidjet and the second (device) liquid jet (and hence upstream of the(first) collision point). In further embodiments a further liquid jet(or liquid device jet provided by a liquid providing device) is directedto a further contact point, especially wherein the further collisionpoint is located at one of the liquid device face and the second liquiddevice face (and hence upstream of the (first) collision point). In yetfurther embodiments, the further (device) liquid jet is directed toanother further (a second) contact point, such as a (second) collisionpoint located downstream of the (first) contact (collision) point toimpact the (coalesced) third material, especially the third jet,especially providing a further coalesced material, and especiallypropagating in a further direction. Embodiments comprising more than twoliquid jets may advantageously be combined. Especially, embodimentscomprising more than one contact point may advantageously be combined.These embodiments may comprise a number of in-flight formation processesin series, especially wherein a product of one in-flight formationprocess (e.g. a coalesced material, such as a coalesced third material)may provide one of the (two) (device) liquid jets of another in-flightformation process. In embodiments, the (coalesced) third material in athird direction of a first in-flight process provides the first (orsecond) liquid jet in a first (or second) direction of a secondin-flight process. In further embodiments, one or more of the firstliquid jet and the second liquid jet are the product (i.e. the thirdmaterial or the third jet) of an in-flight formation process. In furtherembodiments, one or more of the first liquid material and the secondliquid material are the product of a formation process described herein,especially of an in-flight or indirect contacting formation process.Especially, the first and the second liquid material may be selectedindependently to be the product of an in-flight formation process and anindirect contacting process (or not being the product of a formationprocess described herein). Hence, the production process may comprise aplurality of in-flight formation processes. The production process mayalso comprise a plurality of indirect contacting formation processes. Inembodiments, the production process comprises at least one in-flightformation process and at least one indirect contacting formationprocess.

Many different embodiments may be provided wherein an uninterrupted(device) liquid jet impacts on an uninterrupted (device) liquid jet ore.g. a droplet train. Also many different embodiments may be providedwherein an interrupted or an intact (device) liquid jet is directed to adevice face and another liquid jet is provided by said device.

In embodiments, a (device) liquid jet comprises a droplet train and saiddroplet train is directed to a product of a first in-flight formationprocess, comprising also a droplet train. In other embodiments, theproduct of a first in-flight formation process comprises a droplet trainand the (device) liquid jet that is directed to said droplet traincomprises an uninterrupted (device) liquid jet, etc.

In embodiments, a further liquid jet is provided to add an additionalencapsulating layer at the coalesced third material. In such embodimentsthe further liquid jet impacts at a location downstream of the (first)contact point at a further contact point or collision point. Especially,in such embodiments the further liquid jet impacts at a locationdownstream of the (first) collision point. In such embodiment, thefurther liquid jet may comprise a further liquid jet material beingidentical to either the first liquid material or the second liquidmaterial or different to both liquid materials. Especially, the fourthliquid material comprises an equal or lower surface tension as comparedto the second liquid jet material (provided in the encapsulating phaseof the coalesced third material).

Hence, the invention also provides the production process, (comprising a“combined formation process”) further comprising: providing in said gasatmosphere a fourth liquid jet directed with a fourth jet direction to asecond contact point, especially a second collision point, in said gasatmosphere, wherein the fourth liquid jet comprises the fourth liquidmaterial; and coalescing the coalesced third material (of the thirdliquid jet) and the fourth liquid material, to provide the coalescedfifth material (“fifth material”) at the second contact point,especially at the second collision point propagating in the fifthdirection, especially wherein the third direction and the fourth jetdirection of the fourth liquid jet have a mutual angle larger than 0°and equal to or smaller than 45. In embodiments, a further coalescedmaterial and the fifth coalesced material are the same.

Especially, the second contact point comprises the second collisionpoint. In further embodiments, the first contact point comprises thefirst collision point. Hence, in embodiments, the invention alsoprovides the production process wherein the in-flight formation processcomprises a combined in-flight formation process, the combined in-flightformation process comprising: providing in said gas atmosphere (i) saidfirst liquid jet directed with said first jet direction to saidcollision point in said gas atmosphere, wherein said first liquid jetcomprises said first liquid material, and (ii) said second liquid jetdirected with said second jet direction to said collision point, whereinsaid second liquid jet comprises said second liquid material, to provide(a third liquid jet comprising) said (coalesced) third material at saidcollision point propagating in said third direction (especially thirdjet direction); and providing in said gas atmosphere a fourth liquid jetdirected with a fourth jet direction to a second collision point in saidgas atmosphere, wherein the fourth liquid jet comprises a fourth liquidmaterial; and coalescing the coalesced third material and the fourthliquid material, to provide a (coalesced) fifth material at the secondcollision point propagating in a fifth direction.

Especially, in specific embodiments the third direction (of the thirdjet) and the fourth jet direction of the fourth liquid jet have a mutualangle larger than 0° and equal to or smaller than 75°, especially equalto or smaller than 60°, such as equal to or larger than 5°, such asequal to or larger than 10°, and equal to or smaller than 45°.Especially, at least one of the first liquid jet and forth liquid jetare provided as uninterrupted liquid jet at said collision points.Further, especially the coalesced third material and the fourth liquidmaterial have different surface tensions.

Especially, contacting the coalesced third material and the fourthliquid material comprises coalescing the coalesced third material andthe fourth liquid material. The second contact point, especially thesecond collision point, may be located downstream (in the third jet) ofthe first contact point (or first collision point). Yet in embodiments,the first contact point, especially the first collision point, and thesecond contact point, especially the second collision point,substantially coincide (see also below). Especially the first contactpoint may substantially coincide with the second collision point,especially the first collision point substantially coincides with thesecond collision point.

In embodiments, such combined formation production process comprises ajet-nozzle mode (or a nozzle-nozzle mode), wherein the second liquidmaterial is provided to (a face of) a liquid providing device providingthe first liquid jet to provide the third material at a (first) contactpoint. In other embodiments, a first liquid jet and a second liquid jetare (both) directed to a (first) collision point, to provide the thirdmaterial at the first collision point. Especially, in embodimentscomprising a series of formation processes, the first formation processmay comprise an indirect contacting formation process. Especially, insuccessive further formation processes two jets collide at a collisionpoint (comprising a contact point). Especially a further formationprocess comprises an in-flight formation process.

Especially, the invention also provides the device as described hereinfurther comprising a fourth liquid container configured to contain afourth device liquid comprising a fourth device liquid material, influid connection with a fourth device liquid providing device comprisinga fourth opening, a fourth liquid transporter configured to transportthe fourth device liquid from the fourth liquid container to the fourthliquid device and through the fourth opening to provide a fourth deviceliquid jet, wherein the fourth device opening is directed to a secondvirtual collision point downstream of said (first) virtual collisionpoint and/or downstream of said (first) contact point. Especially thefourth device liquid jet comprises the fourth liquid jet.

It is surprisingly found that the production process and the device ofthe invention enable rapid production of a variety of shapes. IAMFenables rapid production of, particles, liquid droplets, partly solidparticles, and fibers in various shapes, sizes and comprising various(internal) structures (phases), see e.g. FIGS. 2 and 3. Moreover, usingthe device and process described herein, complex 3-dimensionalstructures comprising the particles may be generated (see below).Especially, in the production process substantially all of the firstmaterial and second material are combined (coalesce) to provide thethird material. Especially, substantially no (first, second, third,etc.) liquid material is lost in the process. Amongst others, this maybe achieved by selecting the dimension of the jets, the materials of thejets, the velocities of the jets, the mutual angle of the jets, etc.,especially as described herein.

In embodiments, the production process provides droplets, includingdroplets that consist of multiple phases or droplets surrounded by asolid shell. In further embodiments, the production process providessubstantially round shaped (at least partly) solidified particles. Yetin a further embodiment, the production process provides fibers.

Especially by selecting the mutual velocity(s) (the velocity of thefirst (device) liquid jet with respect to the second (device) liquid jetand (optionally) the third direction (the third jet) and the fourth(device) liquid jet, i.e. the velocities of the different liquid jets atthe location of collision points), the shape of the one or moreparticles may be controlled. Additionally or alternatively, the shapemay be controlled by selecting the angle between these jets. The mutualangle(s) is (are) especially selected to be larger than 0° and equal toor smaller than 90°, especially at maximum 60°, such as at maximum 45°.In embodiments the mutual angle is selected between 0° and 35°,especially in the range 10°-30°. In other embodiments, the mutualangle(s) is (are) selected in the range of 60-180°, especially in therange of 90-180°, such as in the range of 90-120° or in the range of150-180°. Especially by selecting a large angle (of at least 90°) of theliquid jets colliding, mixing of the materials comprised in therespective liquid jets may be facilitated. Especially, (providing) alarge impact angle (such as 90-180°) may be advantageous for e.g. in-airmixing of two or more liquid materials (comprised by respective liquidjets). Especially mixing may be facilitated because of a highsurface/volume ratio of the small droplets. Additionally oralternatively, the shape of one or more particles may be controlled in ajet-nozzle or a nozzle-nozzle mode by selecting a flux or flow(especially a quantity over a time) of the jet directed to the nozzleface in relation to the flux or flow and/or the velocity of the jetprovided by said nozzle. Especially in a jet-nozzle mode a first liquidmaterial may be entrained by a second liquid jet (at the contact point).Especially, the second liquid jet velocity must be at least equal to thevelocity of the first liquid at the contact point.

In embodiments of the device one or more of a position of the firstdevice opening and a position of the second device opening iscontrollable, wherein the device further comprises an actuatorconfigured to control one or more of the position of the first deviceopening and the position of the second device opening. For instance, byrotating (part of) the first device and/or the second device, the firstand/or second device openings can be positioned in different positionsallowing e.g. different mutual jet angles. In further embodimentspositioning may be done by translation. Especially an actuator isconfigured to translate. Especially such embodiments may allowcontrolling the mutual angle. Such embodiment may also allow controllingpositioning of one of the device openings relative to the device face ofthe other device. Especially such actuator may control a direction of aliquid device jet. Especially such embodiments may (also) allowcontrolling a distance between liquid devices. Such embodiment mayfurther allow configuring a location of the collision point(s),especially relative to a location of a receptor element. Especially,such actuators may control a location of a liquid device jet. Herein, anactuator also may comprise more than one actuator. In some embodiments,one actuator may be configured to control the position of the firstdevice opening. In embodiments, an actuator may be configured to controla position of a liquid (providing) device. Additionally another actuatormay be arranged to control the position of the second opening. In otherembodiments the device comprises one actuator that may control theposition of the first opening and (the position of) the second opening.In further embodiments least one of the devices may rotate about an axisparallel to a respective longitudinal jet axis, allowing to rotating thejet provided by the device about the longitudinal axis. Especially forsuch embodiments, actuators may be configured to provide the rotation.Especially, embodiments of process may comprise controlling at least oneactuator. For instance, the process may be used to provide a (third)material comprising a coil shape (e.g. by rotating a device about anaxis). This (these) actuator(s) may differ from the (modulating)actuator(s) that provide the modulation of one or more of the (device)liquid jets. In embodiments, these actuators may be the sameactuator(s). Especially, the production process described herein maycomprise twining. Herein the term “twining” relates to twisting orintertwining and especially to providing a rotated or twistedconfiguration. Twining may e.g. be provided by rotating the deviceproviding a jet. Twining may also be provided by rotating the coalescedthird (or further) material downstream form the contact point (while notchanging the jets of the first and second liquid material, e.g. byrotating a receptor element receiving the coalesced third (or further)material. In other embodiments twining may e.g. be provided by theimpact of one of the liquid materials on the other at the location ofimpact (see also below). Hence, in embodiments the method may includetwining at least one of the materials around at least another one of thematerials.

Rapid or automated control of the position of the device opening mayfurther enable to selectively impact and coalesce material, such that inone state the first (device) liquid jet collides with the second(device) liquid jet as described above, whereas in another state thefirst (device) liquid jet does not collide onto the second (device)liquid jet. Such embodiments allow for selecting/sorting selected partsof a liquid jet. For example, only droplets (in a droplet train)comprising a (biological) cell can selectively be impacted, or onlyparts of a liquid fiber can be impacted to form fibers of controlledlength.

Alternatively or additionally to controlling the device opening, a(device) jet may be deflected (post-ejection) in order to provide aselective impact (of two (device) liquid jets) and coalescence. Suchselective post-ejection deflection may be achieved using an electricfield, blowing air, etc. In other embodiment the liquid materialcomprises magnetic material and deflection may be provided by a magneticfield. Especially, embodiments (of the device) may comprise a furtheractuator configured to control the deflection, and especially one of the(first, second, or any further) device openings may not be directed tothe respective (virtual) collision point. Especially the actuatorcontrols the locations of collision, especially to provide a collisionof at least two liquid jets a gaseous atmosphere. Hence also other typesof actuators that may control a direction of a liquid jet may becomprised is embodiments as will be understood by the person skilled inthe art.

As discussed above, coalesced material (i.e. products of the in-flightformation process) comprising a substantially round shape may beprovided in embodiments (comprising liquid jets) in a drop jet mode,especially comprising a jet-nozzle mode. Fiber shaped products of thein-flight formation process may be provided in embodiments (comprisingliquid jets) in a jet-jet mode, especially comprising a jet-nozzle mode.In yet other embodiments of the in-flight formation process products maybe provided comprising a shape comprising fiber-like parts as well asround parts, e.g. resembling a pearl-lace. Especially, such shapes maybe provided if an intact liquid jet collides with a modulated liquid jet(e.g. ejected from an actuated nozzle) that is not broken-up jet inseparate droplets. Especially, such shapes may be provided inembodiments configured to arrange the collision point so that the lengthof the modulated liquid jet stream (L), i.e. a minimum length of a lineconnecting the collision point and the origin (upstream side) of themodulated liquid jet (such as the opening of the liquid providingdevice), is smaller than L_(B), and especially larger than 0.1*LB, suchis in the range of (0.5-0.99)*LB, especially in the range of(0.9-0.99)*LB. Hence, in embodiments, one of the liquid jets ismodulated and the collision point is configured such that said liquidjet is an intact, uninterrupted modulated liquid jet at a locationupstream of the collision point up to the collision point, at thecollision point the modulated liquid jet comprises a variable width in adirection perpendicular to the modulated liquid jet direction.Especially, in such embodiments a product of the in-flight formationprocess is provided having an elongated shape comprising a repeatingvariable width pattern in a direction perpendicular to a longitudinalaxis of the product obtainable by the in-flight formation process.

Between different embodiments wherein L<LB, the shape of the product ofthe in-flight formation process may vary greatly. In embodiments whereinL<<LB, substantially elongated products of the in-flight formationprocess comprising a substantial homogeneous width may be provided. Inembodiment wherein L/LB is selected in the range of 0.1-0.5, products ofthe in-flight formation process may be provided having an elongatedshape wherein the width of the particle may vary only slightly in thelongitudinal direction of the particle, and wherein especially arepetition of the changing width is provided in the longitudinaldirection. In embodiments wherein L is configured almost equal to LB,especially wherein 0.95<L<LB, a product of the in-flight formationprocess may be provided having a shape comprising a series ofinterconnected round droplet shapes (comparable to a pearl-lace).

Especially, the shape may be controlled by the (relative) location ofthe collision point (with respect to the location of breakup of thejet), when instabilities become more prominent in the downstreamdirection. Hence, in embodiments, a product of the in-flight formationprocess comprising a determined shape may be provided by selecting theratio L/L_(B) in the range of 0.5-0.99. In other embodiments, thelocation of impact is selected to configure L>LB, to providesubstantially round products of the in-flight formation process.

Additionally, the shape and the size of these products may be controlledby other operating conditions and liquid properties. With respect to theformer, the shape may be controlled by the velocity of the differentliquid jets, the size of the nozzle or opening of the different liquidgenerating devices (generating the jets), the mutual angle, the possiblemodulation (especially the frequency and/or type of modulation) of thedevices (especially the liquid generating devices, especially thenozzle), the distance between the contact point and a receptor element,etc. With respect to the liquid properties, parameters affecting theshape may be the surface tension, the viscosity and the density of theliquid materials, especially the surface tension of the liquid materials(see below). Furthermore, the liquid solidification properties (such asthermal solidification or freezing, precipitation, or chemical orphysical reactions between two or more ejected liquids) may becontrolled to change the post-solidification shape.

Especially, in embodiments comprising the drop jet mode, the product ofthe in-flight formation process may comprise substantially roundparticles or droplets that may be provided if the liquid jet velocity ofthe first liquid jet and the jet velocity of the second liquid jet aresubstantially equal at the moment of impact (at the collision point).Especially, in further embodiments comprising a jet-nozzle mode (and thedrop jet mode), the product of the formation process may comprisesubstantially round particles or droplets that may be provided if a(volume) flux (flow) of the first liquid jet and a (volume) flux (flow)of the second liquid jet are substantially equal at the contact point.In these embodiments, the size of the (coalesced) third material isespecially affected by the size of the nozzle opening ejecting the(modulated) liquid jet. For the indirect contacting formation process,the size of the (coalesced) third material may especially be affected bythe nozzle opening (of the nozzle providing a liquid jet and beingimpacted by the other liquid at the nozzle face). A desired size of theproduct of the in-flight formation process, e.g. particles or droplets,may depend on the further application of the coalesced material.Especially, the size of the respective nozzle opening (generating themodulated liquid jet and the droplet train) may be selected in range of0.1 μm-5 mm, such as 0.1 μm-1.5 mm, especially 1 μm-1 mm. In otherembodiments, the size of the (respective) nozzle opening may be selectedin the range of 0.05 μm-500 μm, such as 0.5 μm-250 μm, especially 1μm-250 μm. Additionally, the size of the droplets in the droplet trainat the location of the collision point may be affected by a degree ofmodulation of the liquid jet. Especially, the frequency of the(modulating) actuator may be selected to configure the size. Herein afrequency may also comprise more than one frequency, especiallyproviding multiple frequencies by a (modulating) actuator may result inmerging of products (droplets) after the collision point, especiallyfurther allowing to control the final product (size). The size of theparticles or droplets provided with the production process may beproportional to the size of the droplets in the droplet train. Hence inembodiments, the size of a nozzle opening may be selected to configurethe size of the particles. Additionally, the modulation of therespective liquid jet may be selected to configure the size of theparticles. The size of the other nozzle opening may especially beselected to configure the layer thickness of the outer part of theproduct of the in-flight formation process. In embodiments of the deviceone or more of a size of the first device opening and a size of thesecond device opening is controllable. Especially different nozzleopening sizes and actuation (frequencies) may be selected to createjanus particles (see further below) using more than two liquid jets.

Especially eccentric or elongated particles may be provided inembodiments wherein the ratio of the uninterrupted jet velocity and theother liquid jet (the droplet train) velocity ≥1.3. Especially, theratio may be selected to be less than 5, such as at maximum 2.5. Atlarger ratios the (coalesced) third material may break because of theimpact of the intact liquid jet, larger ratios may also cause initiallyseparated droplets to be re-connected by the faster jet, especially suchthat a fiber is formed. For ratios <1.3 the provided coalesced (third)material may comprise a substantially round shape. In embodiments, thefirst liquid jet velocity and the second liquid jet velocity aresubstantially the same.

The said surface tension difference between different ejected liquidsespecially enables encapsulation of high surface tension liquids bythose of lower surface tension. Especially, the surface tension of aliquid material may be configured by adding a surface tension modifier.Examples of such surface tension modifiers are alcohols such asmethanol, ethanol, (iso)propanol, (poly) ethylene glycol (PEG),detergents, soaps solvents, biomolecules (i.e. proteins, DNA, etc.),nano/micro particles, perfluorocarbons, polymers, etc. Hence, inembodiments the composition of the first liquid material and the secondliquid material is substantially the same, wherein the one of the liquidmaterials constitutes of the other liquid material with an additionalsmall amount of ethanol to control the surface tension. Especially insuch configuration, one of the liquid materials may comprise 0.1-70 vol.% ethanol, such as 0.5-25 vol. % ethanol, especially 0.5-10 vol. %ethanol. Especially 0.5-1.5 vol. % ethanol may already be sufficient toprovide a surface tension difference allowing the one of the liquidmaterials to encapsulate the other liquid material. Yet in otherembodiments, the difference between the first liquid material and thesecond liquid material may be provided by a fraction of polyethyleneglycol, such as 1-25 vol. %, especially 5-20 vol. %. Hence, in furtherembodiments, one of liquid comprises the other liquid (material) plus anadded surface tension modifier, especially wherein the difference incomposition between the two liquid is only the presence of the surfacetension modifier. Especially, by using a surface tension modifier anincrease or a decrease of the surface tension of one of the liquids maybe controlled, especially allowing one of the liquids to encapsulate theother liquid.

Alternatively or additionally, at least one of the liquid materials mayespecially comprise (a surface tension modifier as) a functionalmaterial such as biological cell material, e.g. stem cells, proteins andDNA, to be comprised in the third material, especially to providematerials with a structural hierarchy (see further below). Especiallydroplets or particles of at least 10 μm may be suitable forcell-containing materials. Especially, the process allows encapsulationof (biological) cells. In embodiments the process comprisesencapsulation of single cells. In further embodiments, the processcomprises the encapsulation of multiple cells.

In yet other embodiments, two immiscible liquids are coalesced (in thegas atmosphere) to enable encapsulation of the high surface-tensionmaterial. For instance, water and a liquid of lower surface tension suchas a liquid comprising oil or fluorocarbon are coalesced. In otherconfigurations, encapsulation with or without solidification is achievedusing different ejected liquids with different viscosities or sizes.

The location and the degree of solidification may be controlled byphysical as well as chemical parameters. Moreover, especially thecomposition of the different liquid phases as well as the finalcomposition of product of the in-flight formation process, the rate ofsolidification, and other physical parameters like the temperature ofthe gaseous atmosphere, and radiation may be selected in embodiments.Especially, the solidification may be induced by a reaction betweenagents in the first liquid material and the second liquid material,especially providing a network. Hence, in embodiments the first liquidmaterial and second liquid material are selected to react with eachother. Especially, the first liquid material and the second liquidmaterial may be selected to physically, chemically, or biologicallyinteract, especially react, with each other. In further embodiments oneor more of the first liquid material and second liquid material comprisea solidifier, especially a cross-linker, for the other liquid material.Especially a solidifier comprises at least one solidifier. A solidifiermay refer to one solidifier in the first liquid material or the secondliquid material. It also may refer to at least one solidifier in boththe first liquid and the second liquid. It may especially refer to asolidifying complex, wherein (at least) one element of the complex iscomprised in the first liquid material and the remainder of the complexis comprised in the second liquid material. After combining the firstand the second liquid material, the solidifying complex may be formed bythe interaction between the first liquid material and the second liquidmaterial. Especially, a solidifier comprises a cross-linker. Especiallyalso a cross-linker comprises at least one cross-linker (complex). Thefirst liquid materials, e.g., may comprise a first part of thecross-linker (complex) and the second liquid material comprises theremainder of the cross-linker (complex). In yet further embodiments,encapsulation of one liquid by the other liquid material is provided bya difference (between the liquid materials) in surface tension or by aviscosity gradient, and especially at least one of the encapsulatedliquid and the encapsulating liquid is solidified.

In an embodiment with three liquid jets, the materials of the firstliquid jet and the second liquid jet may be combined in various waysprior to impact (at a second collision point) with the fourth liquidjet. For example, the first liquid jet (the first liquid material) maybe of lower surface tension than the second liquid jet (the secondliquid material) to encapsulate the second liquid jet (the second liquidmaterial), after which one or both liquids are solidified by the fourthliquid jet (the fourth liquid material) configured with a lower surfacetension than the first and the second liquid jets (materials). Inembodiments, collision of the first liquid jet and the second liquid jet(in a drop-drop mode or a drop jet mode) providing the third material,that successively may collide with the fourth liquid jet, core-shellparticles may be provided having one or more concentric shells that mayor may not solidify (depending on the material properties). Suchcore-shell particles may also be provided in further embodiments,wherein the first liquid material and the second liquid material contacteach other at a contact point (of an indirect contacting formationprocess) providing the third material, that successively may collidewith the fourth liquid jet. In other embodiments wherein the three jetsare uninterrupted jets, (partly) solidification may provide concentricfibers. Alternatively, the first liquid jet and second liquid jet (thefirst and second liquid material) may be selected to have an equalsurface tension, and especially (after the first collision point) thethird material (the third jet in the third direction) may comprise a“janus” jet. Such janus jet (the third jet) e.g. comprises acylinder-shape, in which a part (of the volume of the jet) comprises thefirst liquid material and another part (comprising the remainder (of thevolume)) comprises the second material. These (coalesced) parts areseparated (partitioned) by a (flat) interface (that may or may not besubstantial parallel to the third direction (a longitudinal axis ofjanus jet)). A further liquid jet, a fourth liquid jet having a lowsurface tension may be directed to impact (at the second collisionpoint) the third jet before or after break-up of the third jet. If thefurther (fourth) liquid jet impacts prior to break-up, a janus fiber maybe provided. If the further (fourth) liquid jet impacts after break-up,janus particles may be formed, especially comprising two distinguishableparts, especially two half-spheres that consist of different materials,see e.g. FIG. 3. Especially, by selecting alternative combinations ofsurface tensions, viscosities, densities, or solidification properties,a wide range of particle or fiber shapes may be produced. Inembodiments, especially for providing janus particles, three jets may beprovided (especially a first, a second, and a further liquid jet).Especially, in such embodiments, the first liquid material and thesecond liquid material have substantially the same equal surfacetensions, especially wherein the further liquid material may have asurface tension different (especially lower) from said surface tension(of the first and/or second material)

Especially, multiple jets may be pointed at a main jet from differentdirections or at different impact locations, for example for scaling-upof the production process. For example, pointing 3 streams of water withalginate droplets at a single, thicker jet consisting of water, ethanol,and CaCl₂ may enable a triple production of cross-linked alginateparticles. Even further, multiple immiscible jets may enable formationof particles with multiple liquid or solid shells, for example byformation of a core-shell particle that impacts onto a further liquidjet of even lower surface tension and is coated again—this procedure canbe repeated multiple times in order to create multiple shells.

Especially the term “main jet” may (also) be related to a (main) jetcomprising a plurality of jets, especially comprising a changingcomposition in a longitudinal direction: starting upstream with a mainjet comprising a first jet, a second jet may contact the main jetproviding a third jet, hence providing the main jet to comprise thethird material (provided by the first jet material and the second jetmaterial). Next (further downstream) providing a further jet to contactthe (main jet) comprising the third material may provide a jetcomprising the forth material. Especially, said jet may also be referredto as main jet (further downstream of the main jet comprising only thethird material), etc. Hence a main jet may “grow” in its longitudinaldirection. Especially a device opening may provide the origin of a mainjet, especially the downstream side of the main jet may substantiallycoincide with the product of the formation process.

In further embodiments, a plurality of second jets (a second jetcomprising a plurality of second jets) comprising a second liquidmaterial are impacted at the (same) collision point at a first jet (suchas a main jet) comprising a first liquid material, wherein the first jetcomprises a cross-linker for the second liquid material. In suchembodiments a plurality of fibers may be provided parallel to each other(each fiber related to one (or a number) of the second jets). Especiallyby selecting the surface tension of the first liquid material lower thanthe second liquid material, fibers may be provided. Especially in suchembodiment, the first liquid (jet) may function as a depot (storage)comprising first liquid material comprising cross-linker material,wherein the first liquid material may envelop (a) second liquid jet(s)and may solidify the second liquid jet(s). Further embodiments comprisetwining. Twining may for instance comprise spinning or twisting the(solidified) second liquid jets, especially to provide spun fibers.Especially embodiments wherein a second contact point and optionally anyfurther contact point coincide(s) with a first contact point maycomprise twining.

An increase in liquid viscosity of the inner and outer liquid (such asof the main jet and of the plurality of jets) may affect aMarangoni-driven flow. This surface-tension driven encapsulation may notalways be fast enough to cover (encapsulate) a droplet for high viscousliquids. Increasing the number of jets may further provide anencapsulation where Marangoni-driven flow is insufficient. Hence, in afurther embodiment the first and second liquid material comprise aviscous material, having a viscosity e.g. in the range of equal to orlarger than 10 mPa·s, especially equal to or large than 100 mPa·s, evenmore especially equal to or larger than 1 Pa·s. Especially in suchembodiment a plurality of (second) jets (comprising the second liquidmaterial) may be impacted at a (the same) collision point at a main jet(comprising the first liquid material), especially comprising a droplettrain.

In yet further embodiments, especially related to the combined formationprocess the plurality of jets are impacted at the main jet at aplurality of collision points distributed in an axial direction of themain jet. In further embodiments, the plurality of jets may point at adifferent location at the main jet (collision points), especiallywherein the collision points are positioned at the main jet, especiallynot at a center of the main jet. The impact of the multiple jets mayprovide a small impact on the main jet. Especially in such embodimentsthe impact may provide a rotation of the main jet, allowing e.g., toprovide twisted fibers, such as comprising a coil-shape, such as aDNA-type of coil shape.

In embodiments comprising a plurality of (second) jets, a productcomprising a plurality (optionally the same) layers may be provided,e.g. when the surface tension of the first liquid material is smaller orequal to the surface tension of the second liquid material. Especiallyembodiments comprising a plurality of (second) jets may easily bescaled-up.

In an embodiment the first liquid material comprises water with calciumchloride and the second liquid material comprises water with ethanol andalginate to provide particles comprising water encapsulated bywater/ethanol. In the gaseous atmosphere the particles solidify when thecalcium chloride migrates (diffuses) from the inner part towards thealginate in the outer part, providing particles comprising a liquidinner part and a solidified outer part, because the alginate solidifieswhen merged with CaCl₂.

In embodiments, the inner part comprises a core, and the outer partcomprises a shell. Especially the particles described herein comprise acore and a shell.

Especially, one or more of the first liquid material and the secondliquid material are solidifiable. Solidification may be a time consumingprocess. Hence, particles (or parts of particles, such as the core orthe shell) may only be partly solidified right after collision, whereasafter a period of time, the solidification may only have completed.Especially, if the solidification in the shell is not completed yet, theproduction process may provide the product of the (in-flight) formationprocess comprising particles that may fuse together when they arecollected in a collector or, e.g., deposited on a surface (see alsobelow) and contact each other. In embodiments wherein the particles arecollected in a (collecting) liquid, an emulsion may be provided. Hence,in embodiments of the production process, the particulate materialcomprises an emulsion, especially wherein the particles are collected ina (collection) liquid. Especially said liquid does not dissolve theparticles. Hence, in embodiments, the product of the in-flight formationprocess comprises a liquid material, wherein the process comprisesreceiving said product of the in-flight formation process in a liquidphase with which the product of the in-flight formation process is notmiscible. In embodiments, the receptor element comprises a liquid. Forinstance, in this way also a dispersion may be provided as(intermediate) product.

Hence, in embodiments, the product of the formation process comprises aliquid material, and the process comprises receiving said product of theformation process in a liquid phase with which the product of theformation process is not miscible. In other embodiments, the processcomprises receiving said product of the formation process in a liquidphase with which the product of the formation process is miscible.Especially, the process comprises receiving the product of the processand/or the coalesced (third) material in a liquid phase. In yet otherembodiments, the process comprises receiving the product of theformation process on to a solid phase, especially wherein the product ofthe formation process comprises a liquid material.

In embodiments, the product of the formation process and the coalescedthird material are the same. In further embodiments, the product of theformation process comprises a further coalesced material, such as afifth coalesced material.

Yet in further embodiments, one liquid material comprises a first activeagent that can diffuse from the outer part into the inner part, and theother liquid material comprises a second active agent that can diffusefrom the inner part to the outer part, wherein a particle that issolidified in the outer part and in the inner part may be provided.Alternatively or additionally the production process may comprise agentsin one or more of the liquid materials that may react under theinfluence of emitted radiation, such as light, especially UV-light, andproviding radiation to the coalesced material to solidify the material.Additionally or alternatively, the first and second liquid materialphase may comprise enzymatically active agents or initiate eitherphysical solidification (e.g., by temperature, precipitation, drying,etc.) or chemical solidification (such as photoinitiated, supramolecularcomplexation, covalent binding, enzyme-mediated, etc.). Especially, if areaction between two agents, such as the enzymatic reaction, is a slowreaction, it may be advantageously if the liquid materials (also)comprise other agents. Especially, the other agents may provide a(first) solidification and immobilization. Especially in such system theformer reaction successively may proceed in the already (partly)solidified particle. In embodiments wherein cross-linking may beenzyme-mediated, cross-linking (and solidification) may be affected bythe enzymatic activity. Especially such enzymatic activity, may becontrolled by (controlling diffusion of) essential co-factors, e.g.hydrogen peroxide for peroxidase or Ca²⁺ in relation to factor XIII.Hence, in embodiments cross-linking may be controlled by a controlleduse of cofactors. In embodiments, cofactors may easily diffuse from onephase to the other.

In yet further embodiments, the products of the in-flight formationprocess are levitated, especially to extend the period to allowsolidification (before received at a receptor element) or any otherreaction. Especially levitation may be provided by directing a gas in adirection opposite to the gravity. Levitation may also be provided byother forces, e.g. electromagnetic forces. In further embodiments adistance between the contact point and the receptor is element isconfigured adjustable. Especially by configuring said distance a (degreeof) solidification may be provided. In other embodiments, (a degree of)encapsulation is provided by configuring said distance. Said distancemay further provide a shape of the product of the formation process.Especially a long distance between the contact point and the receptorelement may provide a third (or further) material breaking up beforecontacting the receptor element.

Especially a jet comprising the coalesced (third or further) materialmay also comprise a breaking length (LB). In embodiments, the distancebetween the contact point and the receptor element is selected to belarger than said breaking length. In embodiments said distance isconfigured to be smaller than said breaking length. In furtherembodiments said distance is selected to be less than or equal to 50% ofsaid the breaking length. The latter embodiments may e.g. provide fiberscomprising a straight configuration.

In embodiments the product of the (in-flight) formation processcomprises a core-shell material. Especially such embodiments may beadvantageously being combined with embodiments wherein the productionprocess comprises receiving said (core-shell) product of the in-flightformation process in a liquid phase which is a solvent for the shell.Such embodiment may also advantageously be combined with embodimentswherein the production process comprises receiving said (core-shell)product of the in-flight formation process in a liquid phase which is asolvent for the core. Especially the first combinations allow theproduction of material that may benefit from a temporary immobilization(by the shell). Especially the latter combination of embodiments mayallow the production of porous material.

In further embodiments, the first liquid phase may comprise a firstactive agent that may react with a second active agent, wherein thesecond liquid phase comprises said second active agent, and at least oneof the liquid phases comprises a third active agent that may react witha forth active agent comprised in a collector or at a receptor element.Especially in such an embodiment (partly) solidified particles may beprovided and collected in the collector (at the receptor element),wherein a further reaction between the third active agent and the secondactive agent may take place in the collector, providing a furthernetwork. In further embodiments, the first and second active agents maybe removed again from the particulate material, e.g. by dissolving theactive agents. An example of such embodiment is an embodiment wherein adroplet train comprises an alginate and a synthetic or natural polymerconjugated with tyramine residues produced in a production process togenerate these materials (known to a person skilled in the art). (Anexample of such material is dextran conjugated with tyramine.) When suchdroplet train of alginate with dextran-tyramine is impacted by a liquidjet comprising CaCl₂ to provide particles (and hence solidify because ofthe alginate —CaCl₂ interaction), and wherein these particles arecollected in a liquid comprising a crosslinking agent fordextran-tyramine to form an interpenetrating network of alginate anddextran-tyramine, and wherein subsequently the alginate from theparticles is dissolved using a calcium chelator, particulate materialcomprising a dextran-tyramine micro gels may be provided. Especiallysuch templating approach enables oil-free production of complex-shapedmicro-particles of arbitrary hydrogels. Especially, such processcomprises receiving the product of the formation process in a liquidphase with which the product of the formation process is miscible,especially providing a further product (of the formation process).Additionally, an in-air solidying shell may be used to maintain adistinct solid precursor spherically shaped after collection (i.e. acore shell comprising an “in-air” formed shell). Hence, the propertiesof the receptor may control the configuration of the product of theformation process. In embodiments, the coaleced (third or further)material is received in a bath, especially in a bath comprising areceptor liquid. Especially, the properties of the receptor liquid maydefine the final product properties. For instance relevant propertiesmay be the chemical composition of said liquid, the surface tension ofsaid liquid, the temperature of said liquid, the viscosity of saidliquid, etc. Especially the properties of said liquid may determine adegree of interaction with the coalesced (third or further) materialreceived in said liquid.

In yet other embodiments the outer part (of the core-shell (in-flight)particles or fibers) immobilizes the inner part, wherein neither theouter part, nor the inner part may solidify. In embodiments, e.g. oneliquid material comprises oil (and a surfactant lowering the surfacetension) and the other liquid material comprises water. Especially suchembodiments may provide coalesced material comprising dropletscomprising an aqueous inner part and an oily outer part. Advantageously,these droplets may be collected in a liquid, especially in an aqueousliquid, to provide a double emulsion. Hence, in embodiments, theproduction process provides a double emulsion, especially awater/oil/water emulsion.

The production process and device described herein may especially beadvantageous for the generation of complex 3-dimensional bodies. Inembodiments, the device comprises a receptor element configured toreceive a product of an in-flight formation process, especial executedwith the device as described herein. As described above differentparticles may be generated comprising a solidified core and/or asolidified shell. Solidification may be complete in embodiments when theparticles are collected. In other embodiments solidification may not yetbe complete when the particles are collected. Especially, by configuringthe distance between the contact point and the receptor element a degreeof solidification may be provided. Especially, these differentcharacteristics allow the generation of materials with a structuralhierarchy, which can be realized in various architectures, especially inembodiments comprising deposition of (or receiving) the coalescedmaterial at a substrate or in a mold. In embodiments, the productionprocess comprises receiving said product of the in-flight formationprocess in a mold. In other embodiments, at least part of the product ofthe in-flight formation process solidifies during propagating to a solidor semi solid, wherein the production process comprises receiving saidproduct of the in-flight formation process at a receptor element,especially a substrate. In embodiments, a core of a core-shell particlemay at least partly be solidified when receiving the particle at or in asubstrate or receptor element (including a mold). Alternatively oradditionally a shell of a core-shell particle my at least be partlysolidified when receiving the particle at or in a substrate (including amold). In further embodiments, the product of the formation process issubstantially in a liquid phase when received or deposited at asubstrate, and especially said product may solidify at the substrate.Especially, a receptor element comprises a substrate or a mold.

In embodiments, products of the in-flight formation process, especiallyfibers, are deposited into a mold, providing a particulate materialcomprising a shape of a mold. In other embodiments the products aredeposited at a substrate, wherein the position of the substrate ischanged in time to provide a determined shape of the final productmaterial. In further embodiments a plurality of jets is impacted at thesame collision point, allowing to direct the third direction, especiallyto provide a determined deposition location of the product (at thesubstrate). Especially, by selecting a specific composition of the firstand/or the second liquid material, in such embodiments particles may beprovided comprising a partly solidified shell that may fuse togetherafter deposition at the substrate or receptor element. Especially, areceptor element may comprise a substrate and/or a mold and/or acollector and/or a collector surface.

Hence, in embodiments the production process comprises depositing theparticulate material at a depositing surface to provide the productcomprising a three dimensional body, or a two-dimensional shape, e.g.for coating a further material. In further embodiments, the depositingsurface is arranged (in time) relative to one (or more) of the liquidgenerating devices, especially to provide a shape of thethree-dimensional object (or a two-dimensional shape, especially to coatanother surface or another 3D body). In embodiments a device positioningsystem is configured to arrange the receptor element relative to one ofthe liquid generating devices to generate the three-dimensional body(from the product of an in-flight formation process, such as aparticulate material, fibrous material, droplets, etc.). Especially, areceptor element, selected from the group consisting of a mold and asubstrate is moved during in-flight formation process for 3D-printing a3D-printed object, for patterning, or e.g. for coating a surface. Yetfurther embodiments, configured for 3D-printing a 3D-printed object, forpatterning or coating a surface, further comprise an actuator configuredto move the receptor element, selected from the group consisting of amold and a substrate, during execution of the in-flight formationprocess. Especially, to deposit (or receive) the product of an in-lineformation process at a determined location, the location may be movedrelative to the remainder of the device. Hence, e.g., also the deviceopening may be repositioned while not moving the receptor element. Inother embodiments the receptor element as well as other parts of thedevice are moved to receive the product at a determined location. Thereceptor element may be actuated. It is further understood thatespecially the properties of the receptor element may define aconfiguration of the (3D) printed object. The configuration may e.g. beprovided by a surface topography of the receptor element. In otherembodiments, the configuration of the printed object is configured by acharge or the temperature of the receptor element. In furtherembodiments, adhesive characteristics or repulsive characteristics of acombination of the receptor element and the coalesced (third or further)material is selected to provide a configuration of the product of theformation

After deposition, further processing may be applied, including heating(including a (partial) melting), washing, drying, etc.

In embodiments, the device is a handheld device, especially facilitatingthe 3D-printing process. In a further embodiment, the device is ahandheld device, especially configured for in situ, especially in vivo,printing of a 3D-body.

In embodiments comprising the drop-jet mode particles comprising a densesuspensions or emulsions deposited on the depositing surface areprovided. Here especially the high throughput of IAMF is expected to bea key benefit.

Injectable shape-stable bodies comprising a structural hierarchy may begenerated by combining a rapidly solidifying core and a slowlysolidifying shell. Especially, after dispositioning, particles or fibersare fused by their still-liquid shell, which solidifies only after astationary situation is reached at the dispositioning surface. Theseinjectable bodies may have a well-controlled microstructure and can bereadily employed to fill a cavity. Such an approach is highly relevantfor filling molds or defects, such as (focal) cartilage defects(cartilage repairs) or skin wounds, but also for injection molding e.g.in-air mixed plastics. Furthermore, post-impact solidifications alsoaids e.g. smooth coating. Alternatively, constructs with a wide range ofshapes and surface finishes can be produced by loosening theseconstructs from a pre-defined mold. IAMF thus enables the production ofsolid hierarchical constructs in virtually arbitrary shapes, similar toexisting casting techniques.

By introducing a rapidly solidifying shell and using a non-solidifyingcore, porous, liquid-filled structures can be deposited in one step.Microfluidic approaches to make such monodisperse foams may normallyrequire to first form and subsequently solidify a porous structure,which is a highly non-trivial and relatively slow process. In contrast,IAMF allows high-throughput deposition of each pore in a predefinedshape. Therefore, IAMF may aid studying the elasticity and failure ofthese closed cell, fluid-filled, solid foams, which have a geometrysimilar to fruits and vegetables. In general, fluid filled solid foamsrecapitulate the structure of natural materials. Also extracellularmatrix of native animal tissue.

Finally and most importantly, one-step printing (deposition) ofhierarchical, free-standing solid structures may be achieved bycombining a rapidly solidifying shell and a slowly solidifying core. Insuch embodiments, the shell of the particles already partiallysolidifies in-air and therefore maintains its shape upon dispositioningat the surface, to constitute a 3D body. Especially, one-step printingmay comprise a plurality of (second) jets directing a location fordepositing a product. Especially one-step printing may comprise aplurality contact points (especially collision points) that coincidedirecting a location for depositing a product. In embodiments, theformation process comprises one-step printing. Especially in suchembodiments, the product of the formation process is deposited onto asolid phase, especially a solid material, such as a plate, or in a cupor container, a table (of an apparatus), or any other type of receptorelement.

In embodiments of the method and device, especially multiple jets mayfurther be integrated in state of the art droplet and/or jet basedmethods and devices. For instance a liquid jet may be configured at FACSor inkjet printing to provide an IAMF compatible device. Embodiments ofthe device and the method may (further) be used in one or more of theapplications selected from the group consisting of cell spraying inendoscopic procedures, pesticide applications, spray coatingapplications, (commercial) production of oil-free core-shell particlesm,rapid printing of 3D multi-component materials or materials withhierarchical morphologies (such as biological tissues), (commercial)production of monodisperse foams, and production of liquid/liquid orsolid/liquid emulsions in food (such as mayonnaise or milk), cosmetics(cream, shampoo), and pharmaceutics, especially related to an improveddroplet or particle size-control and optional particle shape-control.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich: FIG. 1 schematically depicts an embodiment of the device; FIG. 2schematically depicts aspect of the process; FIG. 3 schematicallydepicts some products that may be provided with the method and device;FIGS. 4-9 schematically depicts some further aspects of the process andthe device. Schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The production process and the device of the invention are explainedreferring to FIG. 1. and FIG. 8. FIG. 1 schematically depicts anembodiment of the device 1 (“apparatus”) for a production processcomprising an in-flight formation process. FIG. 8 schematically depictsan embodiment comprising an indirect contacting. For the formationprocess, these embodiments may be combined, see e.g. FIG. 6. Theformation process of the invention comprises contacting a first liquidmaterial 19 and a second liquid material 29 with each other at a contactpoint 180 in a gas atmosphere 5, wherein at the contact point 180 atleast one of the first liquid material 19 and the second liquid material29 is provided as a liquid jet propagating in a direction, to provide atthe contact point 180 a coalesced third material 39 propagating in athird direction 36. The coalesced third material 39 especially providesa third liquid jet 30. Hence, especially the first liquid jet 10 and thesecond liquid jet 20 do not atomize, or provide a mist or a screencomprising the third material 39. Especially, the first liquid jet 10and the second liquid jet 20 provide a further jet, the third liquid jet30, when colliding. Especially, the first liquid material and the secondliquid material do not bounce at the collision point 80.

As is schematically depicted in In FIG. 1, a product 1000 is produced inthe gaseous atmosphere 5. The device 1 comprises a first liquidcontainer 120 comprising a first device liquid 110, comprising a firstdevice liquid material 111 and a second liquid container 220 comprisinga second device liquid 210 comprising a second device liquid material211. In the given embodiment, a first device liquid jet 10 is providedby a first liquid transporter 150 configured to transport the firstdevice liquid 110 from the first liquid container 120 to a first liquidproviding device 100 and through a first device opening 101 in the firstliquid providing device 100. A second device liquid jet 20 is providedby a second liquid transporter 250 configured to transport the seconddevice liquid 210 from the second liquid container 220 to the secondliquid providing device 200 and through a second device opening 201 inthe second liquid providing device 200. In other embodiments only one ofthe (device) liquid materials is provided as a jet. The first liquidproviding device 100 and the second liquid providing device 200 areespecially arranged to allow the first device liquid material 111 andthe second liquid device material 211 to contact each other at thecontact point 180. Especially, the first device opening 101 and thesecond device opening 201 are directed to the contact point 180comprising a (virtual) collision point 80. In the depicted embodimentthe first device 101 opening and the second device opening 201 aredirected to the (virtual) (first) collision point 80, in line of sightof both device openings 101, 201, wherein the device openings 101, 201and the (virtual) (first) collision point 80 define an angle (Θ) largerthan 0° and especially equal to or smaller than 45°. In the depictedembodiment, the contact point 180 is remote from the device openings101, 201. Yet in other embodiments, comprising an indirect contactformation process (see FIG. 8.) the contact point 180 is configuredsubstantially at one of the device openings 101, 201. It is noted that acontact point or a collision point 80 may not be a distinct1-dimensional point. A contact point 180 and a collision point 80 asdescribed herein may comprise a small volume V wherein the liquidmaterials/jets contact each other. A virtual contact point may be adistinct 1-dimensional point. However if liquid material “arrives” atsuch distinct point a small volume will be comprised by the liquidmaterials contacting each other. Such a volume V is schematically andexaggeratedly depicted in the FIG. 6.

One or more of the device openings may be a coaxial device opening,which may be used to provide a coaxial jet of two fluids, especially twodifferent fluids, of which at least one fluid is a liquid.

The device liquid jet 10 comprises an uninterrupted, intact jet 13. Thedevice liquid jets 10, 20 may also comprise a modulated jet 11,schematically depicted by the second device liquid jet 20. Liquid jetsespecially may break up after a certain jet breaking length LB. Amodulated jet 11 may break up more easily. To facilitate break-up, thedevice 1 may comprise one or more (modulating) actuators 50 configuredto provide one or more of a modulated first device liquid jet 10 andsecond device liquid jet 20. The actuator 50 may comprise an element 51configured to vibrate, also referred herein as a “vibrating element” 51.In the embodiment depicted in FIG. 1 the device 1 comprises one(modulating) actuator 50 that provides a modulation of the second deviceliquid jet 20, as may be observed from a variable width Wj in adirection perpendicular to the respective jet direction 15, 26. Themodulated jet 11 breaks up at the breaking length LB. In the depictedembodiment this breaking length LB is shorter than the length L of thejet at the (virtual) (first) collision point 80, i.e. the distance Lfrom the respective device opening 201 to the virtual collision point80. Especially, for a third jet 30, the length L of the jet may bedefined as the distance between the (first) contact point 80 to the endof the jet 30, being the second contact point 185 (see below) in thedepicted embodiment. In other embodiments the coalesced third material39 is directly received by a receptor element 90 and the length L of thethird jet may be defined by the distance between the contact point 80and the receptor element 90. Especially, in such embodiment therespective device liquid jet 20 comprises droplets (i.e. a droplet train12) at the location 80 of impact (the (first) collision point 80) withthe first device liquid jet 10. The liquid providing devices 100, 200 inthe present embodiment may be configured to control the position 102 ofthe first device opening 101 and/or the position 202 of the seconddevice opening 201 to control (the location of) the collision point 80relative to the positions 102, 202 of the respective device openings101, 201. This way the angle Θ between the first device liquid jet 10and the second device liquid jet 20 may be configured. This way also theratio LB/L may be configured. Between different embodiments whereinL<LB, the shape of the product produced with the device 1 may varygreatly. In embodiments wherein L<<LB, substantially elongated productsof the in-flight formation process comprising a substantial homogeneouswidth may be provided. In embodiment wherein L/LB is selected in therange of 0.1-0.5, products of the in-flight formation process may beprovided having an elongated shape wherein the width of the product 1000may vary only slightly in the longitudinal direction of the product1000, and wherein especially a repetition of the changing width isprovided in the longitudinal direction, see e.g. FIG. 3. In embodimentswherein L is configured almost equal to LB, especially wherein0.95<L<L_(B), a product 1000 may be provided having a shape comprising aseries of interconnected round droplet shapes (comparable to apearl-lace), see e.g. FIG. 4. In this embodiments, the device 1especially is configured to provide one of more of said modulated firstdevice liquid jet 10 and second device liquid jet 20 with the respectivejet 11 breaking into subunits after a breaking length LB determined fromthe respective device opening 101,201, wherein the breaking length LB isshorter than L. Especially the device 1 may comprise one or moreactuators 70 configured to control one or more of the position 102 ofthe first device opening 101 and the position 202 of the second deviceopening 201.

In embodiments of the device 1, such as the one depicted in FIG. 1, thedevice further comprising a fourth liquid container 420 configured tocontain a fourth device liquid 410 comprising a fourth device liquidmaterial 411, in fluid connection with a fourth liquid providing device400 comprising a fourth device opening 401, a fourth liquid transporter450 configured to transport the fourth device liquid 410 from the fourthliquid container 420 to the fourth liquid providing device 400 andthrough the fourth device opening 401 to provide a fourth device liquidjet 40. This fourth device opening 401 is directed to a second virtualcollision point 85 downstream of the virtual first collision point 80.By providing the fourth device liquid jet 40, this liquid jet 40 mayfurther collide with the product, i.e. the third material 39—in thethird jet 30 in the third direction 36—provided by the collision of thefirst device liquid jet 10 and the second device liquid jet 20.Especially two in-flight formation processes are configured in series.In the depicted embodiment, the product 1000 of the in-flight process(esin series) is received at a receptor element 90, such as a substrate, amold, or in other embodiments a bath comprising a liquid. In otherembodiments comprising only two liquid device jets 10, 20, the receptorelement 90 may be arranged at a different location. Especially, thedevice 1 may comprise actuator 60 configured to move the receptorelement 90 (directly or indirectly) relative to the remainder of thedevice 1 (for clarity reasons, schematically only pictured in connectionwith the receptor element 90, however the actor 60 may also be connectedto the remainder of the device 1). Hence either the remainder of thedevice and/or the receptor element 90 may be moved to provide theproduct 1000 at a determined position, e.g. to provide 2D or 3D productshapes. The receptor element 90 may also be moved to control a distancebetween the contact point(s) 180, 185, especially the second contactpoint 185 for the depicted embodiment. Especially by controlling saiddistance a process time of the formation process may be configured.Especially by selecting said distance, a determined configuration of theproduct 1000 may be provided. For instance a degree of solidificationmay be provided. Especially the receptor element 90 is configured on atable 91.

Referring to the same FIG. 1, the production process comprising anin-flight formation process may be explained. As already noted in thesummary of the invention, the terms “first”, “second”, “third” and thelike in the description and in the claims, are used for distinguishingbetween similar elements and not necessarily for describing a sequentialor chronological order.

For instance, related to the top of the figure, the first liquidproviding device 100 of the device 1 may comprise the first liquidmaterial 19 or the second liquid material 29. The second liquidproviding device 200 may e.g. comprise the first liquid material 19 ifthe first liquid providing device 100 comprises the second liquidmaterial 29. Analogously, also the first liquid device jet 20 may be thefirst liquid jet, but alternatively the first liquid device jet 20 maybe the second liquid jet, and vice versa. Especially in theseconfigurations, the first liquid jet and the second liquid jet collideat the collision point 80, and the angle between the direction of thefirst liquid and the second liquid is the angle Θ. The figure, however,also depicts the process referring to other (device) jets, jet materialetc.

For instance, the first liquid jet may also comprise the third jet 30and the second liquid jet may be the fourth device liquid jet 40,wherein the first liquid jet and the second liquid jet collide at the(second virtual) collision point 85, and wherein the mutual anglebetween the direction of the first liquid jet and the second liquid jetis the angle Θ″.

For clarity, in the depicted embodiment, the first liquid jet is thefirst device liquid jet 10, comprising the first liquid material 19, andthe second liquid jet 20 is the second device liquid jet, comprising thesecond liquid material 29. Hence, also the first liquid jet may bereferred to by reference number 10, and the second liquid jet isreferred to by reference number 20. Further, this choice implies thatthe mutual angle between the first jet direction and the second jetdirection is equal to the angle Θ defined by the first and second deviceopenings 101, 201 and the virtual collision point 80. Hence also thisangle is referred to by the reference sign Θ.

The formation process of the invention comprises contacting a firstliquid material 19 and a second liquid material 29 with each other at acontact point 180 in a gas atmosphere 5. Especially, at the contactpoint 180 at least one of the first liquid material 19 and the secondliquid material 29 is provided as a liquid jet propagating in adirection to provide a coalesced third material 39 at the contact point180, especially propagating in a third direction 36.

Especially, the in-flight formation process of the invention comprisesproviding in a gas atmosphere 5 a first liquid jet 10 directed with afirst jet direction 16 to a (virtual) (first) collision point 80 in saidgas atmosphere 5, wherein the first liquid jet comprises a first liquidmaterial 19, and a second liquid jet 20 directed with a second jetdirection 26 to the collision point 80, wherein the second liquid jet 20comprises a second liquid material 29 to provide a (coalesced) thirdmaterial 39 at the collision point 80 propagating in a third direction36; wherein the first jet direction 16 of the first liquid jet 10 andthe second jet direction 26 of the second liquid 20 jet have a mutualangle Θ. Especially this angle Θ is larger than 0° and equal to orsmaller than 45°.

Especially, the (production) process comprises providing at least one ofthe first liquid jet 10 and second liquid jet 20 as uninterrupted liquidjet 13 at said collision point, see FIG. 1. In a jet-jet mode (notshown), also the other liquid jet 10, 20 is provided as an uninterruptedliquid jet 13 at the collision point 80. In a drop-jet mode as shown inFIG. 1 one of the liquid jets 10, 20 comprises a droplet train 12 at thelocation of impact 80. Especially, the production process may comprisesmodulating one of the first liquid 10 and the second liquid jet 20 forproviding one of these jets as interrupted liquid jet 12 at saidcollision point 80. Especially, modulating a liquid jet may compriseproviding a vibration to that jet. In a drop-drop mode (also not shown)both liquid jets 10, 20 comprise a droplet train 12 at the collisionpoint 80.

Especially the first liquid material 19 and second liquid material 29may react with each other, e.g. physically, chemically, or biologically,for instance by congealing together, reacting together, an enzymaticreaction, etc.

FIG. 1 schematically depicts an embodiment of the production process,wherein the in-flight formation process comprises a combined in-flightformation process, as will be further explained below, referring to FIG.6.

Especially the process comprises an impact between a first liquidmaterial 19 and a second liquid material 29 having a difference insurface tension. Especially, the ratio of the different surface tensionsis at least 1.005 and not more than 7. At the collision point 80, thefirst liquid material 19 and second liquid material 29 may coalescebecause of this difference in surface tension, wherein the liquidmaterial with the lowest surface tension may encapsulate the liquidmaterial other material, see FIG. 2, schematically showing from the leftto the right a scheme of impact, encapsulation, and solidificationmechanisms. Here, the first liquid material 19 encapsulates the secondliquid material 29. After (partly) solidification a round shaped product1000, especially a particle 1000, may be provided comprising a core 1001and a shell 1002. Solidification may be a time controlled process as isshown by a partly solidified core initially having a solidificationthickness δs, whereas finally the complete core is solidified.Alternatively or additionally, in other embodiments, the shell maysolidify. As is explained above the degree of solidification may forexample be controlled by adjusting the distance between the contactpoint 180 and the receptor element 90,

In FIGS. 3 and 4 some examples of possible products of the process aredepicted. In FIG. 3 various products 1000 with added complexity (top tobottom) are depicted. These products 1000, also referred to as “baseunits” 1050 may commonly be produced using different embodiments of theprocess. At the top simple, single-phase units are shown. In the center“Janus” units, referring to a 2-sided fiber or particle are shown. Janusfibers may have more than two materials which are “stacked” so that theyall have a face at the surface. At the bottom “core-shell” units aredepicted that may be present in four possible phase configurations: (a)double emulsions that comprise a liquid core and a liquid shell; (b)core-shell particles that comprise a liquid core with a solid shell; (c)core-shell particles that comprise a solid core and a solid shell, and(d) comprising a solid core with a liquid shell. Especially one or moreof the first liquid material 19 and second liquid material 29 maycomprise a solidifier, such as a cross-linker for the other liquidmaterial 19, 29 to provide these possible phase configurations.Additionally or alternatively, one or more of the first liquid material19 and the second liquid material 29 are solidifiable. In embodimentsproducts 1000 are received in a liquid phase which is a solvent for theshell and/or the core, especially allowing to produce shell-lessproducts (comprising only a core) or porous particles (comprising only ashell). Especially the shapes of the products 1000 may be controlled byamong others the location of the collision point(s) 80, 85 (providinge.g. the jet-jet, drop jet or drop-drop mode), the velocity of thedifferent jets at the collision point(s) 80, 85, and the liquid material10, 20, 30, . . . properties. In FIGS. 4a-4c , the effect of the ratioL/LB is shown, wherein one of the two different liquid jets 10, 20 ismodulated. The three products at the top (FIGS. 4A, 4B, and 4C) areprovided with increasing L/LB. From the left to the right forrespectively L<<LB, L/LB<0.9, and L˜LB (wherein L being just smallerthan LB). FIG. 4c shows a pearl-lace shaped product 1000. A furtherincrease of L/LB will result in a drop jet mode, providing e.g. productsshown at the bottom in FIGS. 4d and 4e . These two pictures at thebottom show the effect of difference in liquid velocity of the firstliquid jet 10 and the second liquid jet 20, wherein the processcomprises the drop jet mode. Especially increasing the difference invelocity may provide elongated droplets at the collision point 80,providing elongated products 1000 (compare FIG. 4e to FIG. 4d ).

In FIG. 5 a picture of a 3D body 1100 is given produced by devicedescribed herein (see also experimental section). The 3D body 1100 isprovided by an embodiment of the production process comprising receivingthe product 1000 of the in-flight formation process in a mold.Especially, a rapidly solidifying core and a liquid shell enablesinjection of (partly) solid structures. At the left hand side (FIG. 5a )the body 1100 is shown after release from the mold. In the middle (FIG.5b ) the zoomed image shows that the cell-containing fibers 1200 aremostly collected far from the edge of the body 1200. The detail image atthe right (FIG. 5c ) shows that an outer matrix 1150 contains the fibers1200, which in turn contain cells 1250.

In FIG. 6 some embodiments comprising the in-flight formation process inseries is schematically depicted. In other embodiments at least onein-flight formation process and at least one indirect contactingformation process may be arranged in series. In FIG. 6b an embodimentrelated to a combined (in-flight) formation process is depicted. In FIG.6a a production process, wherein one or more of the first liquid jet 10and the second liquid jet 20 are the product of another formationprocess, here an in-flight formation process, is depicted. In furtheradvantageous embodiments these embodiments may be combined. In yetfurther embodiments one or more of the first liquid jet 10 and thesecond liquid jet 20 is the product of an indirect contacting formationprocess. In the embodiment of FIG. 6a , the first liquid jet 10 collideswith a second liquid jet 20. This second liquid jet 20 comprisesessentially a (coalesced) third material 39′, provided by another firstliquid jet 10′ and another second liquid jet 20′, of another (preceding)in-flight formation process. In embodiments the angle Θ between thefirst jet direction 16 and the second jet direction 26 may becontrolled. Also the angel Θ′ between the direction of the other firstliquid jet 10′ and the other second liquid jet 20′ may be controlled.The angles Θ, Θ′ may differ from each other. Especially the embodimentshows both in-flight formation processes in jet-jet mode. In otherembodiments other modes may be used.

The embodiment related to a combined formation process, FIG. 6b depictsa combined in-flight formation process, comprising a fourth (device)liquid jet 40 directed with a fourth jet direction 46 to a secondcontact point 185 comprising a second collision point 85 in said gasatmosphere 5 with the third material 39, wherein the fourth liquid jet40 comprises a fourth liquid material 49. After collision of the thirdmaterial 39 and the fourth liquid jet 40 at the second collision point85, the third material 39 and the fourth liquid material 49 may combine,especially coalesce to provide a (coalesced) fifth material 59 at thesecond collision point 85 propagating in a fifth direction 56, whereinthe third direction 36 of the third jet 30 and the fourth jet direction46 have a mutual angle Θ″ larger than 0° and especially equal to orsmaller than 45°. In the figure also schematically a length of the thirdjet 30 and a breaking length LB of the third liquid jet 30 is depicted.Especially, the third jet 30 may also be characterized as a modulatedjet 11, showing a variable width Wj in a direction perpendicular to thejet direction 36. In other embodiments (also comprising an indirectcontacting formation process), the third material 39 may be directed toa face of another liquid device providing the fourth liquid jet 49through an opening of said other liquid device, and contact that jet 49at the second contact point 185 to provide the fifth material 59 at thatsecond contact point 185. Especially wherein said second contact pointis configured at the opening of said other liquid device, or downstream(with respect to jet 49) thereof. In the embodiment depicted in FIG. 6bthe first liquid providing device 100 providing the first liquid jet 10and or the second liquid providing device 200 providing the secondliquid jet 20 may comprise a (modulating) actuator 50. In the depictedembodiment, e.g., the second liquid providing device 200 comprises anelement 51 configured to vibrate. It is noted that also in suchembodiment the second liquid jet 20 does not have to be interrupted jetat the (first) collision point 80, and still may comprise anuninterrupted, jet. Moreover, especially the second liquid jet 20 maycomprise a modulated liquid jet, provided by the (modulating) actuator50/vibrating element 51 at the second liquid providing device 200, atthe collision point 80, and especially the third liquid jet 30 maybreak-up because of the actuation of the second liquid jet 20. Henceactuating the one of the colliding liquids jets, such as the firstliquid jet 10 and/or the second liquid jet 20, may provide a breakup offormed (coalesced) liquid jet, especially the third liquid jet 30.

In yet further embodiments the first contact point 180 and the secondcontact point 185 coincide, especially the first collision point 80 andthe second collision point 85 may coincide. Such embodiments may e.g.provide the third material 39 comprising parallel fibers. Parallelfibers may in embodiments be twisted. Especially, embodiments of theinvention also comprise twining.

In further embodiments, the production process comprises twining atleast one of the materials 19,29,39,49 (especially, the first liquidmaterial 19, the second liquid material 29, the third material 39, andthe forth material 49) around at least another one of the materials19,29,39,49.

In FIG. 7 the result of an experiment are depicted showing sizedistributions curves, wherein the fraction P at the y-axis as a functionof the size (diameter) at the x-axis of droplets in droplet comprisingthird material 39 provided by a drop jet mode as a function of the sizeof the opening 101, 201 of the liquid providing devices 100, 200. Alsothe effect of the modulation of the drop train providing jet isdepicted. In the experiment, the size of the openings 101, 102 is set at20, 50, 100, and 250 nm, resulting in the distribution curves shown withdifferent line styles respectively from the left to the right hand side(broken with dots, broken, intact, and dotted curves). At the opening of100 nm the modulation is also changed, by changing the frequency ofactuation. Increasing frequency resulted in a more homogeneous sizedistribution, and a decrease in droplet size, as is illustrated by theshift in the intact curves towards a smaller droplet size and a smallerdistribution.

In FIG. 8, an embodiment of the device 1 (and the formation process,especially the indirect contacting formation process) is schematicallydepicted, showing a first device liquid jet 10 (provided by the firstliquid providing device 100) providing a first device liquid material111, especially a first device liquid 19, to the second device face 205at a position above the second device opening 201. The first deviceliquid 110 wets the second device face 205 and may temporarilyaccumulate at the second device face 205, depending e.g. on the materialproperties of the second device face 205 in relation to the propertiesof the first liquid material 19. The surface of the face 205, may e.g.comprise hydrophilic properties. In other embodiments, the second devicesurface 205 may comprise hydrophobic properties. The second deviceopening 201 provides a second device liquid jet (not shown since thelength of the jet is substantially zero) comprising second liquidmaterial 29 that, when contacting the first liquid material 19 at thecontact point 180 may drag along the first liquid material 19 to providethe third jet 30 comprising the coalesced third material 39. Especiallythe contact point 180 is configured at the second device opening 201. Infurther embodiments (not depicted) the first liquid device opening 101is configured in physical contact with the second device face 205. Thefigure, especially schematically depicts a jet-nozzle mode, wherein afirst jet 10 impacts a nozzle, especially a second device face 205. Infurther embodiments opening 101 of the first nozzle may physicallycontact the second device face 205. Especially the later embodimentsrelate to a nozzle-nozzle mode

FIG. 9 schematically depicts an embodiment comprising a plurality ofsecond liquid jets directed 20 to the mutual collision point 80comprising the contact point 180. In the depicted embodiment the angle Θdefined by the first device opening 100 and the respective second deviceopening 201 is alike. In other embodiments, these angles Θ may differfrom each other. Especially having additional second liquid jets 20 mayease scaling up of the process. It may also allow to control the thirddirection 36 of the third jet 30, e.g. allowing to direct the locationto deposit the third material 39 at a receptor element 90, especially toconfigure the product 1000 of the formation process The direction maye.g. be controlled by changing the angles Θ of the respective seconddevices 200. The direction may also be controlled by changing the flowof the respective second liquid jets 20. Especially, such embodimentsmay also provide fibers. Especially by rotating e.g. one or more of thereceptor element 90 and the liquid providing device 100, 200, the fibersmay be rotated and/or twisted, wherein the process especially comprisestwining. Also, in embodiments comprising more than two colliding jets,one or more of the jets may be modulated, especially one or more of theliquid providing devices 100, 200 may comprise a modulating actuator 50.

EXPERIMENTAL

Experiments are described wherein a first liquid jet and a second liquidjet collide at a (first) collision point.

Device Preparation and Operation:

Liquid jets were ejected from nozzle tips of specified diameters. Thenozzle tip consisted of 4±1 mm long fused silica tubing (IdexHealth&Science, Bristol, Conn., USA) with an outer diameter of 360 μmand inner diameters of 20 μm, 50 μm, 100 μm, 150 μm, or 250 μm. Thesetips were cut using a Shortix capillary cutter (SGT, Singapore), andglued into PEEK tubing (Idex H&S) with an inner diameter of 0.5 mm andan outer diameter of 1/16″, using a quick set epoxy adhesive (RS850-956, RS components Ltd., Corby, UK). The PEEK tubing was stuck andclamped to the (modulating) actuator using two-sided tape (3M) andstandard optical components (Thorlabs, Newton, N.J., USA), respectively.For actuation, a piezo-electric element was used, to which a sine waveof high voltage (150V) was applied. For various nozzle sizes and flowrates, jet breakup into droplets was monitored using a stroboscopicvisualization setup. This approach enabled to fine-tune the actuationfrequency for stable jet break-up. Unless otherwise specified, flowvelocities of 1.3±0.2× the minimum flow velocity (below which drippingoccurs instead of jetting) were applied. It is noted that, at theminimum flow velocity a liquid Weber number We₁ may equal 1. The liquidWeber number, We₁ being defined as ρ_(l)V²D/σ_(l), with ρ_(l), V, σ_(l)being the density, velocity and surface tension of the liquidrespectively, and D being the diameter of the jet or of a droplet in thejet.

These velocities were found to yield the most stable jet break-up whilestill allowing for well-controlled in-air processing. Both nozzles (asrequired for the two jets or droplet trains) were of equal diameter, andoperated at equal velocity unless otherwise specified. The respectiveposition of the nozzles was controlled by mounting one of the nozzlesonto a 3D stage with 1 μm-precision (Thorlabs). In the hand-held device,a screw was used to deflect the nozzle tip. Rotating this screw(diameter M4) allowed for precise aiming of the two liquid jets,enabling their in-air coalescence. To control the flow rate, a standardsyringe pump (type PhD 2000, Harvard Apparatus, Holliston, Mass., USA)and plastic syringes were used (5 ml or 10 ml, Luer-Lok, BD, FranklinLakes, N.J., USA). A high-power syringe pump (Harvard Apparatus) andsteel syringes (9 ml, Harvard Apparatus) were used in case excessivepressure drops over the nozzle tip caused the standard syringe pump tostall (i.e. mainly for the 20 μm nozzles). Threaded adapters (Idex H&S)were used to connect the syringes to the PEEK tubing in which the nozzletips were glued as described.

Reagents

The following liquids were used to generate various materials:

Default configuration, used unless otherwise specified.

Liquid 1 (droplet train/jet): 0.5% (w/v) sodium alginate (80 to 120 cP,Wako Chemicals) solution. Liquid 2 (jet): A 0.1M CaCl₂ in a 10% (vol.)Ethanol solution. Liquid 3 (bath): A 0.03M CaCl₂ solution.

Water-oil emulsions: Liquid 1: Water. Liquid 2: Surfactant containingperfluorocarbon oil (2% Pico-Surf 1 in Novec 7500, Dolomite, Royston,UK) PicoSurf. Liquid 3: PerFluor Perfluorocarbon oil+one dropPico-Surf 1. Liquid 3: PerFluor+drop of picosurf.

Double emulsions (water-oil-water): Liquid 1: Water. Liquid 2: PicoSurf.Liquid 3: Water+1% Sodium dodecyl sulfate (SDS).

Liquid-filled core-shell particles and liquid-filled foams: Liquid 1: A0.2M CaCl₂+5% PEG400 solution. Liquid 2: A 0.4% sodium alginate (5 to 40cP, Sigma-Aldrich)+20% Ethanol. Liquid 3: A 0.03M CaCl₂ solution.

Solid-filled core-shell particles and hierarchical SFF: Liquid 1: A 0.2MCaCl₂+5% PEG400 solution. To be completed Liquid 2: A 0.4% sodiumalginate (5 to 40 cP, Sigma-Aldrich)+20% Ethanol. Liquid 3: A 0.03MCaCl₂ solution.

Hierarchical injectable: Liquid 1: A 0.2M CaCl₂+5% PEG400 solution.Liquid 2: A 0.4% sodium alginate (5 to 40 cP, Sigma-Aldrich)+20%Ethanol. Liquid 3: A 0.03M CaCl₂ solution.

For visualization purposes, <0.1% of dextran-FITC (2000 kDa,Sigma-Aldrich, St. Louis, Mo., USA), Rhodamine B dye, or rhodamineB-stained particles (500 nm diameter) were added to the liquid to bevisualized.

Cell isolation, expansion and encapsulation: Human mesenchymal stemcells (MSCs) were isolated from fresh bone marrow samples and cultured.The use of patient material was approved by the local ethical committeeof the Medisch Spectrum Twente and informed written consent was obtainedfor all samples. In short, nucleated cells in the bone marrow aspirateswere counted, seeded in tissue culture flasks at a density of 5*10⁵cells/cm² and cultured in MSC proliferation medium, consisting of 10%(v/v) fetal bovine serum (FBS, Lonza), 100 U/ml Penicillin with 100mg/ml Streptomycin (Gibco), 2 mM L-Glutamine (Gibco), 0.2 mM ascorbicacid and 1 ng/ml basic fibroblast growth factor (ISOKine bFGF,Neuromics) in Minimal Essential Medium (MEM) α with nucleosides (Gibco).MSCs were cultured under 5% CO₂ at 37° C. and medium was replaced 2 to 3times per week. When cell culture reached near confluence, the cellswere detached using 0.25% Trypsin-EDTA (Gibco) at 37° C. andsubsequently subcultured or used for experimentation. For cellencapsulation, MSCs were suspended in MSC proliferation medium and mixedwith 1% (w/v) sodium alginate (80 to 120 cP, Wako Chemicals) inphosphate-buffered saline (PBS, Gibco) in a 1:1 ratio. The cell-ladenhydrogel precursor solution was loaded into a disposable syringe andconnected to the IAMF setup for micro gel production. Afterencapsulation, cell-laden micro gels were cultured in 6-wells plates(Nunc) with MSC proliferation medium under 5% CO₂ at 37° C. Viability ofencapsulated MSCs was analyzed using a live/dead assay (MolecularProbes) following manufacturers protocol and visualization using afluorescence microscope (EVOS FL, Thermo Fisher Scientific). Images wereanalyzed using ImageJ software and cell viability was quantified viaartisan counting.

Protocol for Washing/Collecting Micro Gels:

1) Add 1 ml PBS+CaCl₂ Eppendorf.

2) Collect ˜500 μl micro gels+cross linker solution.

3) If necessary, wash 3× with tap water and 2× with PBS+CaCl₂ (e.g. toremove background fluorescence).

Washing procedure: Spin down micro gels using 3 short spins in microcentrifuge. Remove 1 ml supernatant. Add 1 ml fresh solution.

Surface Tension Measurement:

The surface tensions of various (Water+0.1M CaCl₂)—ethanol mixtures weremeasured by the hanging drop method, using a Dataphysics OCA15Prooptical contact angle measuring system. The ethanol volume fraction isdefined as f=V₁/(V₁+V₂), where V₁ and V₂ refer to the volumes of unmixedethanol and water−CaCl₂, respectively. The results overlap previousmeasurements for ethanol-water mixtures within the experimental error(5%), indicating that the presence of CaCl₂ hardly affects the surfacetension of the mixed liquid.

Results

Here, monodisperse droplets are generated by controlled breakup of theliquid jet ejected from nozzle 1. This droplet train impacts onto anintact liquid jet that is ejected from nozzle 2, resulting in a compoundmonodisperse droplet train flowing downwards. Subsequently, aftertypically ˜100 ms in our experiments, the compound droplets arecollected in a bath or deposited onto a solid surface. Alternatively,the setup can be operated in “jet-jet mode”. This mode enables to spinfibers, by solidifying one of the liquids prior to breakup of the mergedjet. Finally, we operated the system in “drop-drop mode”, but found thismode more challenging than the drop jet mode while not addingfunctionality, and therefore abandoned this direction. Still, thephysical mechanisms governing drop-drop mode are relatively well-studiedand also apply to the other modes, which we exploit in the following.First, the droplet impacts onto the jet. Since a significant ejectionvelocity is required for jet formation, a small impact angle Θ=25°±5°was chosen to ensure a low impact Weber number. Experiments where thedroplet is selectively colored, confirmed that the droplets maintaintheir spherical shape during impact. For We_(impact)˜1 (the horizontalvector of the Weber number), the coalescence is capillary driven and theimpact occurs on a capillary time scale τ_(cap)=(ρD₁ ³σ₁/μ₁)^(1/2) inwhich D₁, σ₁, and μ₁ are the diameter of the droplets, and the surfacetension and the viscosity of the liquid in the droplets (in the droplettrain) respectively. The advantageous method that may prevent thedroplets from merging during flight is to provide their encapsulation bythe jet. Subsequently, encapsulation of the droplets by the jet wasachieved by lowering the surface tension of the encapsulating (jet)liquid by adding a small amount of ethanol. As a result, Marangoni flow(i.e. driven by surface tension gradients) pulls a thin film of the lowsurface-tension liquid (of the jet) around the high surface-tensionliquid (of the droplet), as depicted in FIG. 2. Our state-of-the-artvisualization techniques revealed the encapsulation process. The processoccurs on a numerically validated time scale τ_(e)˜σ₁ Oh₁ τ_(cap)/Δσ,with Δσ=σ₁-σ₂ and σ₂ the surface tension of the liquid jet, and whereinOh₁=μ₁/(ρ₁σ₁D₁)^(1/2) is the Ohnesorge number in which μ₁ is thedroplet's viscosity. For our experimental conditions, τ_(e) iscomparable to the impact time scale τ_(cap). Therefore, both impact andencapsulation are completed in the air, prior to collection ordeposition which may typically happen at a timescale of about 1 ms-100ms after in-air impact.

Finally, solidification of the droplets enabled the production ofparticles. In particular, the inner and outer liquids could be chosensuch that one or both of them solidified. Here we usedalginate-containing droplets and CaCl₂ jets a model system to freeze thedroplets in-air, since alginate solidifies when merged with CaCl₂.

By introducing a surface tension gradient Δσ, the particle shape couldbe tuned from irregular (Δσ=0 mN/m) to spherical (Δσ>5 mN/m). The regimetransition from irregular to regular, especially spherical particles wasobserved at a Δσ=5 mN/m, as achieved by adding a minimal amount of 0.3%ethanol. In alternative embodiments, e.g. comprising alternative dropletsizes and/or liquids this threshold may be varied between 0.2 mN/m to1000 mN/m.

It is surprising that the particle shape may be controlled by combiningsurface-tension-driven encapsulation and solidification, as even a thinsolid front could potentially inhibit the Marangoni flow. To provide afirst rationalization of this observation, we hypothesize thatencapsulation is achieved if the surface tension gradient exceeds thestrength of the solidifying film. The thickness of this film isestimated as δ_(s)˜(D_(s) τ_(s))^(1/2), with D_(s)˜10⁻⁹ m²s⁻¹ theeffective diffusion constant of the solidification front. The strengthof the film is estimated as σ_(f)·δ_(s), where σ_(f)=10⁴ Pa is thefracture stress of a 0.5% alginate gel. By equating σ_(f)·δ_(s) andsolving for Δσ, one may determine a transition Δσ as a function ofnozzle diameter at which the obtained shape changes from irregular shapeto regular shape. For the measured parameter regime, the expected filmstrength lies between 2 mN/m and 5 mN/m, which is remarkably close tothe experimental threshold Δσ=5 mN/m. However, the predicted dependenceon the diameter of the nozzle is not observed, possibly because theinitial solidification dynamics (e.g. temporally increasing viscositieswhile crosslinking) are ignored. Future studies may reveal the detailsof combined Marangoni flow and solidification, which would be applicableto other encapsulation methods as well.

Remarkably, for mass-driven solidification as used in our system,τ_(s)<<τ_(cap) even for extremely thin solid films of thicknessδ/D₁=10⁻². Therefore, solidification was unlikely to interfere with theimpact and encapsulation, but indeed followed these events immediatelyand in-flight.

Visualization of the collected alginate micro-particles reveals thatalginate and CaCl₂ solutions with equal surface tensions results in theformation of irregular, bag-shaped alginate particles. However, adramatic change occurs for droplet encapsulation by a lowsurface-tension jet, which results in spherical particles. We thendetermined the minimal difference in surface tension for in-airencapsulation, by analyzing the shape (bag vs. spherical) of alginatemicro gels with different diameters as a function of the CaCl₂ jetsurface tension. It was demonstrated that, monodisperse spherical microgels with diameters ranging from 20 μm to 250 μm are produced forσ₁/σ₂>1.2, which corresponded to adding only 1% of ethanol to the jet.This implies that relatively weak, but fully cytocompatible alternativesurface tension modifiers such as polyethylene glycol could also aidin-air droplet encapsulation. This safe, versatile and robust approachaids the rapid integration of IAMF in clinical applications.

A limitation of IAMF may be the relatively short in-air time of ˜100 ms.Therefore, only rapidly solidifying hydrogels such as alginate seem tobe suitable for IAMF. To overcome this limitation and thus enable theuse of a wide variety of in-situ cross-linkable hydrogels, we usedalginate as a template. As a proof-of-concept, we solidified dropletsthat consist of an alginate/dextran-tyramine mixture in-air, by impacton a CaCl₂-containing jet (as described). These particles were collectedin a bath containing the crosslinking agent for dextran-tyramine, toform an interpenetrating network of alginate and dextran-tyramine.Subsequently, we dissolved the alginate from the particles using acalcium chelator, leaving only dextran-tyramine micro-gels behind. Thistemplating approach enables oil-free production of complex-shaped microparticles of arbitrary hydrogels. Alternatively, rapid temperature orlight-induced freezing mechanisms can be exploited to solidify materialsin-air.

With a single device droplets, particles, and fibers in various shapes,were prepared. Microfluidic base units were produced in the drop-jetmode; examples are given in FIGS. 3, 4 and in the table given furtherbelow. Coalescing water droplets onto a surfactant containingfluorocarbon oil jet—with lower surface tension—readily enabled theproduction of monodisperse water-in-oil (w/o) emulsions. Moreover,collecting these w/o droplet in sodium dodecyl sulfate (SDS) containingwater resulted in w/o/w double emulsions. However, making the inverseoil-water suspension proved challenging and remains to be realized,since oils generally have a low surface tension. Still, a single IAMFsetup produced both single and double emulsions without the need of ahydrophobic or hydrophilic surface treatment, a typical constraint ofchip-based microfluidics. Furthermore, IAMF also enables direct oil-freeproduction of particles, a proven strategy for the encapsulation offood, drugs and even cells. Here, monodisperse micro particles wereproduced by in-air gelation of alginate droplets by a CaCl₂ and ethanolcontaining jet. Alternatively, by coalescing CaCl₂ droplets onto anethanol containing alginate jet, alginate capsules were produced. Thelatter approach was further explored for the production ofmulti-material core-shell particles. Specifically, we incorporatedenzymatically crosslinkable dextran-tyramine conjugates and horseradishperoxidase into the CaCl₂ containing droplets, while mixing itscorresponding cross linker hydrogen peroxide in the alginate containingjet. This approach enables production of multi-material core-shell microgels. However, the capsules and the multi-material core-shell microparticles frequently result in (undesired) merged particles comprisingmulti-core particles. We hypothesize that the origin of these multi-coreparticles is in-air collision of partly-solidified shells, as observedin the live view of the droplet trains. Such inter-droplet collisionsmay be prevented by further homogenizing the speed and size of thedroplets, for example by optimizing the pump and nozzle design. Therobustness of IAMF with respect to the droplet or particle size wasinvestigated, since size is a key control parameter for virtually anyapplication. Using different nozzles, monodisperse alginate micro gelswith diameters ranging from 20 μm to 300 μm were readily produced. Thesize distributions are plotted in FIG. 7, indicating reasonablemonodispersity for each nozzle size. Furthermore, for a single nozzlediameter, the exact micro gel diameter can be fine-tuned by altering theactuation frequency f, as shown in FIG. 7 for the nozzle diameter of 100μm (for clarity reasons, only a few curves are plotted). Such anapproach may be highly relevant if large nozzles are required but smalldroplets are desired, for example to prevent clogging when dispensingcell-containing liquids. Finally, the typical drop size in IAMF can bereduced much further by using smaller nozzles of e.g. 1 μm. Therefore,IAMF may be rapidly adopted as a microencapsulation technique for foodand pharmacy, where these small drops are widely used.

Shape-controlled fibers and particles are readily produced with the samesetup. Fibers of homogeneous thickness were produced by coalescingalginate and CaCl₂ containing jets before they broke up, thus withoutactuation. Interestingly, with nozzle actuation turned on while movingthe jets' impact location closer to the break-up point (i.e. L→L_(B)),“wavy” fibers with periodic thickness are produced as shown in FIG. 4B.If the jet is solidified even closer to the break-up location L_(B), thefiber resembles a lace of pearls, as shown in FIG. 4C. Finally, ifL>L_(B), the system is again operated in drop jet mode resulting insubstantially round particles. Still, in drop jet mode, shape control ofthe particles was achieved by increasing the jet velocity whilemaintaining constant droplet velocity. In particular, particles with arivulet shape were fabricated for α=V₁/V₂>1, as shown in FIGS. 4d and 4e.

Emulsions, suspensions, and fibers comparable to the presently obtainedresults may also be produced by MF devices and, for particles, byshooting droplets through a liquid sheet. However, our approach has fourdistinct benefits for their production. First, production rates ofdroplets and particles are 100× faster as compared to MF chips (see alsobelow). Second, a single, cost-effective, and hand-held device can beapplied for producing all these units. Third, producing particles isachieved oil-free, which offers distinct advantages for clinical andbiological applications over MF approaches in which oil is required as alubricant. Fourth, IAMF can be readily integrated in equipment where adroplet train is used, such as flow-assisted cell sorters. For thesereasons, we believe that IAMF may finally bring microfluidic functionsto a wide range of applications.

One-Step Printing of 3D Hierarchical Materials

Another novelty of IAMF is one-step deposition of materials with astructural hierarchy, which can be realized in various architectures.The most straightforward implementation is a soft “micro-spaghetti”.Here, fibers were deposited into a mold instead of a bath, wherein themold was moved during depositing. Similarly, operating the IAMF systemin drop jet mode enables rapid production of droplets or particles thatconstitute dense suspensions or emulsions if they are deposited on asolid material. Since these materials can already be produced usingchip-based microfluidics, here the high throughput of IAMF is expectedto be a key benefit.

Second, injectable shape-stable solids with a structural hierarchy areformed by combining a rapidly gelating inner phase, called “core”, and aslowly solidifying outer phase, the “shell”. Here, after impact,particles or fibers are lubricated by their still-liquid shell, whichsolidifies only after a stationary situation is reached. Theseinjectable solids have a well-controlled microstructure and can bereadily employed to fill a cavity. Such an approach is highly relevantfor e.g. cartilage repairs. Alternatively, constructs with a wide rangeof shapes and surface finishes can be produced by loosening theseconstructs from a pre-defined mold, as demonstrated in FIG. 5 thusenables the production of solid hierarchical constructs in virtuallyarbitrary shapes, similar to existing casting techniques.

Third, by introducing a rapidly solidifying shell and using anon-solidifying core, porous, liquid-filled structures are deposited inone step. Microfluidic approaches to make such monodisperse foams enableeven more control of the pore location, but require to first form andsubsequently solidify a porous structure, which is a highly non-trivialand relatively slow process. In contrast, IAMF allows high-throughputdeposition of each pore in a predefined shape. Therefore, IAMF may aidstudying the elasticity and failure of these closed cell, fluid-filled,solid foams, which have a geometry similar to fruits and vegetables.

Finally and most importantly, one-step printing of hierarchical,free-standing solid structures is achieved by combining a rapidlysolidifying shell and a slowly solidifying core. Here, each shellalready partially solidifies in-air and therefore maintains its shapeupon impact, to constitute a 3D construct. Using this technique we wereable to build a hollow construct. In this example, impact onto arotating glass slide resulted in a hollow hydrogel cylinder resembling ablood vessel. But a wide variety of 3D shapes would be available byintegrating the IAMF nozzles in a 3D printer.

Potential Applications of IAMF

The versatility, resolution, throughput, and ease of use of IAMF are nowdiscussed, since these parameters are crucial for applications. First,the versatility can be enhanced even further: By varying the core andshell materials alone, 16 different material topologies can be depositedas summarized in the following table. Especially, most topologies/baseunits may be produced as particles and as fiber. In the table wet impactrelates to receiving the base units in a liquid; whereas dry impactrelates to deposition on a surface or other (dry) receptor element.

Material type Shell Core Wet Dry Pre- Cross- Pre- Cross- impact impactcursor linker cursor linker (Double) Dense O O O O emulsion¹ emulsion⁽¹⁾Particles/ Porous O IF IF O fibers^(1,2) injectable^(1,2) Not stableMulti-solid PI IF IF PI injectable^(1,2) Liquid core - Liquid-filled IFO O IF solid shell^(1,(2)) foam^(1,(2)) Solid core - Hierarchical IF PIPI IF solid shell^(1,(2)) SFF Overview of IAMF material products (leftcolumns) as a function of shell and core gelation properties (rightcolumns); wherein O meaning no solidification; IF meaning in-flightsolidification, and PI post-impact solidification. Superscripts: 1 =Deposition as droplets/particles; 2 = deposition as fibers; wherein useof brackets: no brackets = experimentally demonstrated, brackets = inprinciple possible.

Many more variations can be achieved by for example merging three ormore different liquids in-air, introducing solid particles to the systemor performing more advanced in-air chemistry including combustion. Next,droplets, particles or fibers can be dried in-air to yield a powder,potentially enhancing encapsulation and spray drying technologies aswidely used in the food and pharmaceutical industries. Furthermore,thermal solidification may be exploited instead of gelation, whichalready enabled encapsulation by shooting aqueous droplets through athin sheet of molten wax. Similarly, different driving mechanisms may beexploited for in-air impact and encapsulation. Using and combining thesestrategies may result in entirely different time scales for impact,encapsulation and solidification, and thus enable a tremendous variationof shapes, surface morphologies, and (printed) material properties. IAMFcan be readily used to manufacture 16 different products, when in-flightcoalescence and encapsulation are ensured. These products includeemulsions, particle and fiber suspensions, and hierarchical materialscomprising these particles and fibers. Multi-solid materials aretypically produced by adding one solid precursor solution to thecore-forming jet and its corresponding crosslinker to the shell-formingjet and a second distinct precursor and crosslinker vice versa.

The resolution and throughput of IAMF are compared to other drop-basedand jet-based. A general trade-off between resolution and throughput isvisible, in which in-air technologies such as inkjet printing and(electro) spraying generally score well. On the other hand, versatilityis greatly enhanced by in-line control as used in microfluidics, butusually results in lower throughput. To our best knowledge, IAMFuniquely combines in-air processing with in-line control, which opens anew domain with a minimal traditional trade-off between resolution,throughput, and versatility.

The practical implementation of IAMF can be straightforward. A hand-helddevice allows for all functionality demonstrated here. Such a device iseasy to clean, which benefits clinical translation as well asapplications in food and pharmaceutics. Using such a device, structurescan easily be printed onto surfaces with an arbitrary inclination angle.

For all these reasons, integration of IAMF in technologies that exploitdroplet trains, such as continuous ink-jet printing or flow-assistedcell sorting, may add functionality without requiring major processchanges. Users of droplet microfluidics may exploit the ˜100 timesthroughput increase as offered by IAMF. However, we particularly expectadvances in tissue engineering, where one-step deposition ofmulti-material and hierarchical nature-mimicking tissues is an urgentbottleneck. The material architectures demonstrated in above resemblenatural plant and animal tissues, and are cytocompatible. Therefore,clinical translation of IAMF as well as applications in tissueregeneration and stem cell research are expected to be relativelystraightforward.

In conclusion, we propose IAMF as a strategy to combine the benefits ofdevice-based microfluidics with those of printing technologies. Bymerging reacting liquids in-air, materials that are very different fromthe liquids leaving the nozzles are deposited. This approach has twoparticular benefits. First, it circumvents a trade-off in materialhardness that limits current printing techniques, and therefore allowsdeposition of a much wider range of materials. In particular, IAMFallows for one-step printing of multi-material topologies, as urgentlydemanded in bio fabrication. Second, the lack of a lubricating liquid asused in microfluidic devices enables ˜100 times faster processing ofdroplets and particles (microfluidics already enables fast production offibers). A wide variety of such “base units” was demonstrated, but weexpect to develop more varieties in the future. Finally, IAMF allows foroptical access of in-air chemical processes, can be readily integratedinto existing nozzle-based equipment, and is cost-effective andstraightforward to implement. Therefore, we foresee a major impact onmanufacturing, healthcare, and research.

The term “substantially” herein, such as in “substantially consists”,will be understood by the person skilled in the art. The term“substantially” may also include embodiments with “entirely”,“completely”, “all”, etc. Hence, in embodiments the adjectivesubstantially may also be removed. Where applicable, the term“substantially” may also relate to 90% or higher, such as 95% or higher,especially 99% or higher, even more especially 99.5% or higher,including 100%. The term “comprise” includes also embodiments whereinthe term “comprises” means “consists of”. The term “and/or” especiallyrelates to one or more of the items mentioned before and after “and/or”.For instance, a phrase “item 1 and/or item 2” and similar phrases mayrelate to one or more of item 1 and item 2. The term “comprising” may inan embodiment refer to “consisting of” but may in another embodimentalso refer to “containing at least the defined species and optionallyone or more other species”.

Furthermore, the terms first, second, third and the like in thedescription and in the claims, are used for distinguishing betweensimilar elements and not necessarily for describing a sequential orchronological order. It is to be understood that the terms so used areinterchangeable under appropriate circumstances and that the embodimentsof the invention described herein are capable of operation in othersequences than described or illustrated herein.

The devices herein are amongst others described during operation. Aswill be clear to the person skilled in the art, the invention is notlimited to production process of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe able to design many alternative embodiments without departing fromthe scope of the appended claims. In the claims, any reference signsplaced between parentheses shall not be construed as limiting the claim.Use of the verb “to comprise” and its conjugations does not exclude thepresence of elements or steps other than those stated in a claim. Thearticle “a” or “an” preceding an element does not exclude the presenceof a plurality of such elements. The invention may be implemented bymeans of hardware comprising several distinct elements, and by means ofa suitably programmed computer. In the device claim enumerating severalmeans, several of these means may be embodied by one and the same itemof hardware. The mere fact that certain measures are recited in mutuallydifferent dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage.

The invention further applies to a device comprising one or more of thecharacterizing features described in the description and/or shown in theattached drawings. The invention further pertains to a method or processcomprising one or more of the characterizing features described in thedescription and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order toprovide additional advantages. Further, the person skilled in the artwill understand that embodiments can be combined, and that also morethan two embodiments can be combined. Furthermore, some of the featurescan form the basis for one or more divisional applications.

The invention claimed is:
 1. A production process comprising a formationprocess, the formation process comprising contacting a first liquidmaterial and a second liquid material with each other at a contact pointin a gas atmosphere, wherein, at the contact point, one of the firstliquid material and the second liquid material is provided in aninterrupted first liquid jet propagating in a first direction, wherein,at the contact point, another of the first liquid material and thesecond liquid material is provided in an uninterrupted second liquid jetpropagating in a second direction, wherein, at the contact point, athird jet of a coalesced third material is created, propagating in athird direction; and wherein the first liquid material and the secondliquid material have different surface tensions.
 2. The productionprocess according to the preceding claim 1, comprising an in-flightformation process, the in-flight formation process comprising: providingin the gas atmosphere: (i) a first liquid jet directed with a first jetdirection to a collision point in said gas atmosphere, wherein the firstliquid jet comprises the first liquid material, and (ii) a second liquidjet directed with a second jet direction to the collision point, whereinthe second liquid jet comprises the second liquid material, to providethe coalesced third material at the collision point propagating in thethird direction, wherein the contact point comprises the collisionpoint.
 3. The production process according to claim 2, wherein the firstjet direction of the first liquid jet and the second jet direction ofthe second liquid jet have a mutual angle larger than 0° and equal to orsmaller than 45° , and wherein the process comprises providing at leastone of the first liquid jet and second liquid jet as uninterruptedliquid jet at said collision point.
 4. The production process accordingto claim 2, wherein the production process further comprises providing avibration to one of the first liquid jet and the second liquid jet forproviding one of the first liquid jet and the second liquid jet asinterrupted liquid jet at said collision point, or wherein theproduction process further comprises providing a vibration to one of thefirst liquid jet and the second liquid jet for providing one of thefirst liquid jet and the second liquid jet as uninterrupted liquid jethaving variable width (Wj) in a direction perpendicular to therespective jet direction at said collision point; and wherein thevibration is provided by means of an actuator comprising an elementconfigured to vibrate at a frequency selected from the range of 100 Hz-1MHz.
 5. The production process according to claim 2, wherein one or moreof the first liquid jet and the second liquid jet are the product of anin-flight formation process.
 6. The production process according toclaim 2, wherein one or more of the first liquid material and the secondliquid material are the product of an in-flight formation process or anindirect contacting formation process.
 7. The production processaccording to claim 2, wherein one or more of the first liquid materialand second liquid material comprise a cross-linker for the other liquidmaterial, or wherein one or more of the first liquid material and thesecond liquid material are solidifiable.
 8. The production processaccording to claim 2, the process further comprising: providing in saidgas atmosphere a fourth liquid jet directed with a fourth jet directionto a second collision point in said gas atmosphere, wherein the fourthliquid jet comprises the fourth liquid material; and coalescing thecoalesced third material and the fourth liquid material, to provide thecoalesced fifth material at the second collision point propagating inthe fifth direction, wherein the third direction and the fourth jetdirection of the fourth liquid jet have a mutual angle larger than 0°and equal to or smaller than
 45. 9. The production process according toclaim 8, wherein the first collision point and the second collisionpoint coincide.
 10. The production process according to claim 8,comprising twining at least one of the materials around at least anotherone of the materials.
 11. The production process according to claim 8,wherein the product of the formation process comprises a liquidmaterial, and wherein the process comprises receiving said product ofthe formation process in: (a) a liquid phase with which the product ofthe formation process is not miscible, or (b) a liquid phase with whichthe product of the formation process is miscible, or (c) onto a solidphase.
 12. The production process according to claim 8, wherein one ormore of the following applies: (i) the product of the formation processcomprises a core-shell material, and wherein the production processcomprises receiving said product of the formation process in a liquidphase which is a solvent for the shell or the core; (ii) the productionprocess comprises receiving said product of the formation process in amold; (iii) at least part of the product of the formation processsolidifies during propagating to a solid or semi solid; and (iv) theproduction process comprises receiving said product of the formationprocess at a substrate, and wherein a receptor element, selected fromthe group consisting of the mold and the substrate is moved duringin-flight formation process for 3D-printing a 3D-printed object.
 13. Theproduction process according to claim 1, the process comprising anindirect contacting formation process, the indirect contacting formationprocess comprising: providing a second liquid jet comprising the secondliquid material by a second liquid providing device comprising a seconddevice face and a second device opening, wherein the second liquid jetis directed with a second liquid jet direction, and providing the firstliquid material to the second device face at a position above saidsecond device opening, and allowing the first liquid material and thesecond liquid material to contact with each other at the contact point,wherein the contact point is configured at the second device opening ordownstream thereof.
 14. The production process according to claim 13,wherein the first liquid material is provided by a first liquid jetprovided by a first liquid providing device.
 15. The production processaccording to claim 13, wherein the first liquid material is provided bya first liquid providing device, wherein the first liquid providingdevice a first device opening, wherein the first device opening isconfigured in physical contact with the second device face.
 16. Theproduction process according to claim 1, wherein a ratio of thedifferent surface tensions is at least 1.05 and not more than
 7. 17. Theproduction process according to claim 1, wherein the coalesced thirdmaterial comprises capsules.
 18. The production process according toclaim 17, wherein the capsules are alginate capsules.
 19. The productionprocess according to claim 17, wherein the coalesced third materialfurther comprises core-shell micro particles.
 20. The production processaccording to claim 19, wherein the coalesced third material comprisesmulti-core particles.
 21. The production process according to claim 19,wherein the capsules and the core-shell micro particles comprisemulti-core particles.